Keystroke logging
Encyclopedia
Keystroke logging is the action of tracking (or logging) the keys struck on a keyboard
, typically in a covert manner so that the person using the keyboard is unaware that their actions are being monitored. There are numerous keylogging methods, ranging from hardware and software-based approaches to electromagnetic
and acoustic
analysis.
. From a technical perspective there are five categories:
to capture people's PINs. Each keypress is registered by the keyboard of the ATM as well as the criminal's keypad that is placed over it. The device is designed to look like an integrated part of the machine so that bank customers are unaware of its presence.
can be used to monitor the sound created by someone typing on a computer. Each key on the keyboard makes a subtly different acoustic signature when stroked. It is then possible to identify which keystroke signature relates to which keyboard character via statistical methods
such as frequency analysis
. The repetition frequency of similar acoustic keystroke signatures, the timings between different keyboard strokes and other context information such as the probable language in which the user is writing are used in this analysis to map sounds to letters.
A fairly long recording (1000 or more keystrokes) is required so that a big enough sample
is collected.
of a wired keyboard from up to 20 metres (65.6 ft) away, without being physically wired to it.
In 2009, Swiss researches tested 11 different USB
, PS/2
and laptop keyboards in a semi-anechoic chamber
and found them all vulnerable, primarily because of the prohibitive cost of adding shielding
during manufacture.
The researchers used a wide-band receiver
to tune into the specific frequency of the emissions radiated from the keyboards.
, can allow a criminal to watch a PIN or password being entered.
and posted to the Usenet news group net.unix-wizards,net.sources on November 17, 1983. The posting seems to be a motivating factor in restricting access to /dev/kmem on Unix
systems. The user-mode program operated by locating and dumping character lists (clists) as they were assembled in the Unix kernel.
or as part of a virus
. What is not trivial for an attacker, however, is installing a covert keystroke logger without getting caught and downloading data that has been logged without being traced. An attacker that manually connects to a host machine to download logged keystrokes risks being traced. A trojan that sends keylogged data to a fixed e-mail address or IP address
risks exposing the attacker.
Security & Privacy paper (their paper from '96 touches on it as well). They presented a deniable password snatching attack in which the keystroke logging trojan is installed using a virus or worm. An attacker who is caught with the virus or worm can claim to be a victim. The cryptotrojan asymmetrically encrypts the pilfered login/password pairs using the public key of the trojan author and covertly broadcasts the resulting ciphertext
. They mentioned that the ciphertext can be steganographically
encoded and posted to a public bulletin board such as Usenet
.
s to the last few unused sectors of every writable disk that is inserted into the machine. The sectors remain marked as unused. This can be done using a USB
token. So, the trojan author may be one of dozens or even thousands of people who are given the stolen information. Only the trojan author can decrypt the ciphertext because only the author knows the needed private decryption key. This attack is from the field known as cryptovirology
.
used a keystroke logger to obtain the PGP
passphrase
of Nicodemo Scarfo, Jr.
, son of mob boss Nicodemo Scarfo
.
Also in 2000, the FBI lured two suspected Russian cyber criminals to the US in an elaborate ruse, and captured their usernames and passwords with a keylogger that was covertly installed on a machine that they used to access their computers in Russia. The FBI then used these credentials to hack into the suspects' computers in Russia in order to obtain evidence to prosecute them.
Also, keylogger software authors may be able to update the code to adapt to countermeasures that may have proven to be effective against them.
is a piece of software specifically designed to detect keyloggers on your computer, typically comparing all files in your computer against a database of keyloggers looking for similarities which might signal the presence of a hidden keylogger. As anti keyloggers have been designed specifically to detect keyloggers, they have the potential to be more effective than conventional anti virus software; some anti virus softwares do not consider certain keyloggers a virus, as under some circumstances a keylogger can be considered a legitimate piece of software.
or write-protected Live USB
is a possible countermeasure against software keyloggers if the CD is clean of malware and the operating system contained on it is secured and fully patched so that it cannot be infected as soon as it is started. Booting a different operating system does not impact the use of a hardware or BIOS based keylogger.
, heuristics and keylogger behaviours (such as the use of hooks
and certain API
s).
No software-based anti-spyware application can be 100% effective against all keyloggers.
Also, software-based anti-spyware cannot defeat non-software keyloggers (for example, hardware keyloggers attached to keyboards will always receive keystrokes before any software-based anti-spyware application).
However, the particular technique that the anti-spyware application uses will influence its potential effectiveness against software keyloggers. As a general rule, anti-spyware applications with higher privileges
will defeat keyloggers with lower privileges. For example, a hook-based anti-spyware application cannot defeat a kernel-based keylogger (as the keylogger will receive the keystroke messages before the anti-spyware application), but it could potentially defeat hook- and API-based keyloggers.
(also known as reverse-firewalls) can be used to alert the user whenever an application attempts to make a network connection. This gives the user the chance to prevent the keylogger from "phoning home
" with his or her typed information.
s are primarily designed for web browser
s to fill in checkout pages and log users into their accounts. Once the user's account and credit card
information has been entered into the program, it will be automatically entered into forms without ever using the keyboard or clipboard
, thereby reducing the possibility that private data is being recorded. However someone with physical access to the machine may still be able to install software that is able to intercept this information elsewhere in the operating system or while in transit on the network. (Transport Layer Security
(TLS) prevents the interception of data in transit by network sniffers and proxy tools
.)
s may be keylogger-safe, as each password is invalidated as soon as it's used. This solution may be useful for someone using a public computer, however an attacker who has remote control over such a computer can simply wait for the victim to enter his/her credentials before performing unauthorised transactions on their behalf while their session is active.
One-time passwords also prevent replay attack
s where an attacker uses the old information to impersonate. One example is online banking
where one-time passwords are implemented to protect accounts from keylogging attacks as well as replay attacks. KYPS
is a service that gives OTP access to websites that normally do not offer OTP access.
s or other security token
s may improve security against replay attack
s in the face of a successful keylogging attack, as accessing protected information would require both the (hardware) security token as well as the appropriate password/passphrase. Knowing the keystrokes, mouse actions, display, clipboard etc used on one computer will not subsequently help an attacker gain access to the protected resource. Some security tokens work as a type of hardware-assisted one-time password system, and others implement a cryptographic challenge-response authentication
, which can improve security in a manner conceptually similar to one time passwords. Smartcard readers
and their associated keypads for PIN
entry may be vulnerable to keystoke logging through a so called supply chain attack
where an attacker substitutes the card reader/PIN entry hardware for one which records the user's PIN.
) send normal keyboard event messages to the external target program to type text. Every software keylogger can log these typed characters sent from one program to another.
Additionally, keylogging software can take screenshots of what is displayed on the screen (periodically, and/or upon each mouse click), which means that although certainly a useful security measure, an on-screen keyboard will not protect from all keyloggers.
These programs attempt to trick keyloggers by introducing random keystrokes, although this simply results in the keylogger recording more information than it needs to. An attacker has the task of extracting the keystrokes of interest—the security of this mechanism, specifically how well it stands up to cryptanalysis
, is unclear.
software can also be used against keyloggers, since there are no typing or mouse movements involved. The weakest point of using voice-recognition software may be how the software sends the recognized text to target software after the recognition took place.
s and lately tablet PC
s can already convert pen (also called stylus) movements on their touchscreen
s to computer understandable text successfully. Mouse gestures utilize this principle by using mouse movements instead of a stylus. Mouse gesture programs convert these strokes to user-definable actions, such as typing text. Similarly, graphics tablet
s and light pen
s can be used to input these gestures, however these are less common everyday.
The same potential weakness of speech recognition applies to this technique as well.
s to remove, cut, copy, and paste parts of the typed text without using the keyboard. An attacker who is able to capture only parts of a password will have a smaller key space
to attack if he chose to execute a brute-force attack.
Another very similar technique utilizes the fact that any selected text portion is replaced by the next key typed. E.g. if the password is "secret", one could type "s", then some dummy keys "asdfsd". Then these dummies could be selected with mouse, and next character from the password "e" is typed, which replaces the dummies "asdfsd".
These techniques assume incorrectly that keystroke logging software cannot directly monitor the clipboard, the selected text in a form, or take a screenshot every time a keystroke or mouse click occurs. They may however be effective against some hardware keyloggers.
Keyboard (computing)
In computing, a keyboard is a typewriter-style keyboard, which uses an arrangement of buttons or keys, to act as mechanical levers or electronic switches...
, typically in a covert manner so that the person using the keyboard is unaware that their actions are being monitored. There are numerous keylogging methods, ranging from hardware and software-based approaches to electromagnetic
Electromagnetism
Electromagnetism is one of the four fundamental interactions in nature. The other three are the strong interaction, the weak interaction and gravitation...
and acoustic
Acoustics
Acoustics is the interdisciplinary science that deals with the study of all mechanical waves in gases, liquids, and solids including vibration, sound, ultrasound and infrasound. A scientist who works in the field of acoustics is an acoustician while someone working in the field of acoustics...
analysis.
Software-based keyloggers
These are software programs designed to work on the target computer’s operating systemOperating system
An operating system is a set of programs that manage computer hardware resources and provide common services for application software. The operating system is the most important type of system software in a computer system...
. From a technical perspective there are five categories:
- Hypervisor-based: The keylogger can theoretically reside in a malwareMalwareMalware, short for malicious software, consists of programming that is designed to disrupt or deny operation, gather information that leads to loss of privacy or exploitation, or gain unauthorized access to system resources, or that otherwise exhibits abusive behavior...
hypervisorHypervisorIn computing, a hypervisor, also called virtual machine manager , is one of many hardware virtualization techniques that allow multiple operating systems, termed guests, to run concurrently on a host computer. It is so named because it is conceptually one level higher than a supervisory program...
running underneath the operating system, which remains untouched. It effectively becomes a virtual machineVirtual machineA virtual machine is a "completely isolated guest operating system installation within a normal host operating system". Modern virtual machines are implemented with either software emulation or hardware virtualization or both together.-VM Definitions:A virtual machine is a software...
. Blue PillBlue pill (malware)Blue Pill is the codename for a controversial rootkit based on x86 virtualization. Blue Pill originally required AMD-V virtualization support, but was later ported to support Intel VT-x as well...
is a conceptual example. - KernelKernel (computing)In computing, the kernel is the main component of most computer operating systems; it is a bridge between applications and the actual data processing done at the hardware level. The kernel's responsibilities include managing the system's resources...
-based: This method is difficult both to write and to combat. Such keyloggers reside at the kernel levelRing (computer security)In computer science, hierarchical protection domains, often called protection rings, are a mechanism to protect data and functionality from faults and malicious behaviour . This approach is diametrically opposite to that of capability-based security.Computer operating systems provide different...
and are thus difficult to detect, especially for user-mode applications. They are frequently implemented as rootkitRootkitA rootkit is software that enables continued privileged access to a computer while actively hiding its presence from administrators by subverting standard operating system functionality or other applications...
s that subvert the operating system kernel and gain unauthorized access to the hardware, making them very powerful. A keylogger using this method can act as a keyboard device driverDevice driverIn computing, a device driver or software driver is a computer program allowing higher-level computer programs to interact with a hardware device....
for example, and thus gain access to any information typed on the keyboard as it goes to the operating system. - API-based: These keyloggers hookHookingIn computer programming, the term hooking covers a range of techniques used to alter or augment the behavior of an operating system, of applications, or of other software components by intercepting function calls or messages or events passed between software components...
keyboard APIsApplication programming interfaceAn application programming interface is a source code based specification intended to be used as an interface by software components to communicate with each other...
; the operating system then notifies the keylogger each time a key is pressed and the keylogger simply records it. Windows APIs on such asGetAsyncKeyState,GetForegroundWindow, etc. are used to poll the state of the keyboard or to subscribe to keyboard events. These types of keyloggers are the easiest to write, but where constant polling of each key is required, they can cause a noticeable increase in CPUCentral processing unitThe central processing unit is the portion of a computer system that carries out the instructions of a computer program, to perform the basic arithmetical, logical, and input/output operations of the system. The CPU plays a role somewhat analogous to the brain in the computer. The term has been in...
usage, and can also miss the occasional key. A more recent example simply polls the BIOSBIOSIn IBM PC compatible computers, the basic input/output system , also known as the System BIOS or ROM BIOS , is a de facto standard defining a firmware interface....
for pre-boot authentication PINPersonal identification numberA personal identification number is a secret numeric password shared between a user and a system that can be used to authenticate the user to the system. Typically, the user is required to provide a non-confidential user identifier or token and a confidential PIN to gain access to the system...
s that have not been cleared from memory. - Form grabbing based: Form grabbing-based keyloggers log web formForm (web)A webform on a web page allows a user to enter data that is sent to a server for processing. Webforms resemble paper or database forms because internet users fill out the forms using checkboxes, radio buttons, or text fields...
submissions by recording the web browsing onsubmit event functions. This records form data before it is passed over the Internet and bypasses HTTPS encryption. - Packet analyzers: This involves capturing network traffic associated with HTTP POSTPOST (HTTP)In computing, POST is one of many request methods supported by the HTTP protocol used by the World Wide Web. The POST request method is used when the client needs to send data to the server as part of the request, such as when uploading a file or submitting a completed form.In contrast to the GET...
events to retrieve unencrypted passwords.
Remote access software keyloggers
These are local software keyloggers with an added feature that allows access to the locally recorded data from a remote location. Remote communication may be achieved using one of these methods:- Data is uploaded to a website, database or an FTPFile Transfer ProtocolFile Transfer Protocol is a standard network protocol used to transfer files from one host to another host over a TCP-based network, such as the Internet. FTP is built on a client-server architecture and utilizes separate control and data connections between the client and server...
server. - Data is periodically emailed to a pre-defined email address.
- Data is wirelessWirelessWireless telecommunications is the transfer of information between two or more points that are not physically connected. Distances can be short, such as a few meters for television remote control, or as far as thousands or even millions of kilometers for deep-space radio communications...
ly transmitted by means of an attached hardware system. - The software enables a remote login to the local machine from the Internet or the local network, for data logs stored on the target machine to be accessed.
Related features
Software Keyloggers may be augmented with features that capture user information without relying on keyboard key presses as the sole input. Some of these features include:- Clipboard logging. Anything that has been copied to the clipboardClipboard (software)The clipboard is a software facility that can be used for short-term data storage and/or data transfer between documents or applications, via copy and paste operations...
can be captured by the program. - Screen logging. ScreenshotScreenshotA screenshot , screen capture , screen dump, screengrab , or print screen is an image taken by a computer to record the visible items displayed on the monitor, television, or another visual output device...
s are taken in order to capture graphics-based information. Applications with screen logging abilities may take screenshots of the whole screen, just one application or even just around the mouse cursor. They may take these screenshots periodically or in response to user behaviours (for example, when a user has clicked the mouse). A practical application used by some keyloggers with this screen logging ability is to take small screenshots around where a mouse has just clicked; these defeat web-based keyboards (for example, the web-based screen keyboards that are often used by banks) and any web-based on-screen keyboard without screenshot protection. - Programmatically capturing the text in a control. The Microsoft WindowsMicrosoft WindowsMicrosoft Windows is a series of operating systems produced by Microsoft.Microsoft introduced an operating environment named Windows on November 20, 1985 as an add-on to MS-DOS in response to the growing interest in graphical user interfaces . Microsoft Windows came to dominate the world's personal...
APIApplication programming interfaceAn application programming interface is a source code based specification intended to be used as an interface by software components to communicate with each other...
allows programs to request the text 'value' in some controls. This means that some passwords may be captured, even if they are hidden behind password masks (usually asterisks). - The recording of every program/folder/window opened including a screenshot of each and every website visited, also including a screenshot of each.
- The recording of search engines queriesWeb search queryA web search query is a query that a user enters into web search engine to satisfy his or her information needs. Web search queries are distinctive in that they are unstructured and often ambiguous; they vary greatly from standard query languages which are governed by strict syntax rules.- Types...
, instant messenger conversations, FTP downloads and other Internet-based activities (including the bandwidth used).
Hardware-based keyloggers
Hardware-based keyloggers do not depend upon any software being installed as they exist at a hardware level in a computer system.- Firmware-based: BIOSBIOSIn IBM PC compatible computers, the basic input/output system , also known as the System BIOS or ROM BIOS , is a de facto standard defining a firmware interface....
-level firmwareFirmwareIn electronic systems and computing, firmware is a term often used to denote the fixed, usually rather small, programs and/or data structures that internally control various electronic devices...
that handles keyboard events can be modified to record these events as they are processed. Physical and/or root-level accessSuperuserOn many computer operating systems, the superuser is a special user account used for system administration. Depending on the operating system, the actual name of this account might be: root, administrator or supervisor....
is required to the machine, and the software loaded into the BIOS needs to be created for the specific hardware that it will be running on. - Keyboard hardware: Hardware keyloggers are used for keystroke logging by means of a hardware circuit that is attached somewhere in between the computer keyboardComputer keyboardIn computing, a keyboard is a typewriter-style keyboard, which uses an arrangement of buttons or keys, to act as mechanical levers or electronic switches...
and the computer, typically inline with the keyboard's cable connector. More stealthy implementations can be installed or built into standard keyboards, so that no device is visible on the external cable. Both types log all keyboard activity to their internal memory, which can be subsequently accessed, for example, by typing in a secret key sequence. A hardware keylogger has an advantage over a software solution: it is not dependent on being installed on the target computer's operating system and therefore will not interfere with any program running on the target machine or be detected by any software. However its physical presence may be detected if, for example, it is installed outside the case as an inline device between the computer and the keyboard. Some of these implementations have the ability to be controlled and monitored remotely by means of a wireless communication standard.
Wireless keyboard sniffers
These passive sniffers collect packets of data being transferred from a wireless keyboard and its receiver. As encryption may be used to secure the wireless communications between the two devices, this may need to be cracked beforehand if the transmissions are to be read.Keyboard overlays
Criminals have been known to use keyboard overlays on ATMsAutomated teller machine
An automated teller machine or automatic teller machine, also known as a Cashpoint , cash machine or sometimes a hole in the wall in British English, is a computerised telecommunications device that provides the clients of a financial institution with access to financial transactions in a public...
to capture people's PINs. Each keypress is registered by the keyboard of the ATM as well as the criminal's keypad that is placed over it. The device is designed to look like an integrated part of the machine so that bank customers are unaware of its presence.
Acoustic keyloggers
Acoustic cryptanalysisAcoustic cryptanalysis
Acoustic cryptanalysis is a side channel attack which exploits sounds emitted by computers or machines. Modern acoustic cryptanalysis mostly focuses on sounds emitted by computer keyboards and internal computer components, but historically it has also been applied to impact printers and...
can be used to monitor the sound created by someone typing on a computer. Each key on the keyboard makes a subtly different acoustic signature when stroked. It is then possible to identify which keystroke signature relates to which keyboard character via statistical methods
Statistics
Statistics is the study of the collection, organization, analysis, and interpretation of data. It deals with all aspects of this, including the planning of data collection in terms of the design of surveys and experiments....
such as frequency analysis
Frequency analysis
In cryptanalysis, frequency analysis is the study of the frequency of letters or groups of letters in a ciphertext. The method is used as an aid to breaking classical ciphers....
. The repetition frequency of similar acoustic keystroke signatures, the timings between different keyboard strokes and other context information such as the probable language in which the user is writing are used in this analysis to map sounds to letters.
A fairly long recording (1000 or more keystrokes) is required so that a big enough sample
Sample (statistics)
In statistics, a sample is a subset of a population. Typically, the population is very large, making a census or a complete enumeration of all the values in the population impractical or impossible. The sample represents a subset of manageable size...
is collected.
Electromagnetic emissions
It is possible to capture the electromagnetic emissionsElectromagnetic radiation
Electromagnetic radiation is a form of energy that exhibits wave-like behavior as it travels through space...
of a wired keyboard from up to 20 metres (65.6 ft) away, without being physically wired to it.
In 2009, Swiss researches tested 11 different USB
Universal Serial Bus
USB is an industry standard developed in the mid-1990s that defines the cables, connectors and protocols used in a bus for connection, communication and power supply between computers and electronic devices....
, PS/2
IBM Personal System/2
The Personal System/2 or PS/2 was IBM's third generation of personal computers. The PS/2 line, released to the public in 1987, was created by IBM in an attempt to recapture control of the PC market by introducing an advanced proprietary architecture...
and laptop keyboards in a semi-anechoic chamber
Anechoic chamber
An anechoic chamber is a room designed to stop reflections of either sound or electromagnetic waves.They are also insulated from exterior sources of noise...
and found them all vulnerable, primarily because of the prohibitive cost of adding shielding
Electromagnetic shielding
Electromagnetic shielding is the process of reducing the electromagnetic field in a space by blocking the field with barriers made of conductive and/or magnetic materials. Shielding is typically applied to enclosures to isolate electrical devices from the 'outside world' and to cables to isolate...
during manufacture.
The researchers used a wide-band receiver
Receiver (radio)
A radio receiver converts signals from a radio antenna to a usable form. It uses electronic filters to separate a wanted radio frequency signal from all other signals, the electronic amplifier increases the level suitable for further processing, and finally recovers the desired information through...
to tune into the specific frequency of the emissions radiated from the keyboards.
Optical surveillance
Optical surveillance, while not a keylogger in the classical sense, is nonetheless an approach that can be used to capture passwords or PINs. A strategically placed camera, such as a hidden surveillance camera at an ATMAutomated teller machine
An automated teller machine or automatic teller machine, also known as a Cashpoint , cash machine or sometimes a hole in the wall in British English, is a computerised telecommunications device that provides the clients of a financial institution with access to financial transactions in a public...
, can allow a criminal to watch a PIN or password being entered.
Physical evidence
For a keypad that is used only to enter a security code, the keys which are in actual use will have evidence of use from many fingerprints. A passcode of four digits, if the four digits in question are known, is reduced from 10,000 possibilities to just 24 possibilities. These could then be used on separate occasions for a manual "brute force attack."History
An early keylogger was written by Perry KivolowitzPerry Kivolowitz
Perry Kivolowitz is an American computer scientist and business person. In 1985, he co-founded Advanced Systems Design Group which built hardware for the Commodore Amiga. This company was renamed Elastic Reality, Inc. and became well known as a digital imaging software provider...
and posted to the Usenet news group net.unix-wizards,net.sources on November 17, 1983. The posting seems to be a motivating factor in restricting access to /dev/kmem on Unix
Unix
Unix is a multitasking, multi-user computer operating system originally developed in 1969 by a group of AT&T employees at Bell Labs, including Ken Thompson, Dennis Ritchie, Brian Kernighan, Douglas McIlroy, and Joe Ossanna...
systems. The user-mode program operated by locating and dumping character lists (clists) as they were assembled in the Unix kernel.
Cracking
Writing simple software applications for keylogging can be trivial, and like any nefarious computer program, can be distributed as a trojan horseTrojan horse (computing)
A Trojan horse, or Trojan, is software that appears to perform a desirable function for the user prior to run or install, but steals information or harms the system. The term is derived from the Trojan Horse story in Greek mythology.-Malware:A destructive program that masquerades as a benign...
or as part of a virus
Computer virus
A computer virus is a computer program that can replicate itself and spread from one computer to another. The term "virus" is also commonly but erroneously used to refer to other types of malware, including but not limited to adware and spyware programs that do not have the reproductive ability...
. What is not trivial for an attacker, however, is installing a covert keystroke logger without getting caught and downloading data that has been logged without being traced. An attacker that manually connects to a host machine to download logged keystrokes risks being traced. A trojan that sends keylogged data to a fixed e-mail address or IP address
IP address
An Internet Protocol address is a numerical label assigned to each device participating in a computer network that uses the Internet Protocol for communication. An IP address serves two principal functions: host or network interface identification and location addressing...
risks exposing the attacker.
Trojan
Young and Yung devised several methods for solving this problem and presented them in their 1997 IEEEInstitute of Electrical and Electronics Engineers
The Institute of Electrical and Electronics Engineers is a non-profit professional association headquartered in New York City that is dedicated to advancing technological innovation and excellence...
Security & Privacy paper (their paper from '96 touches on it as well). They presented a deniable password snatching attack in which the keystroke logging trojan is installed using a virus or worm. An attacker who is caught with the virus or worm can claim to be a victim. The cryptotrojan asymmetrically encrypts the pilfered login/password pairs using the public key of the trojan author and covertly broadcasts the resulting ciphertext
Ciphertext
In cryptography, ciphertext is the result of encryption performed on plaintext using an algorithm, called a cipher. Ciphertext is also known as encrypted or encoded information because it contains a form of the original plaintext that is unreadable by a human or computer without the proper cipher...
. They mentioned that the ciphertext can be steganographically
Steganography
Steganography is the art and science of writing hidden messages in such a way that no one, apart from the sender and intended recipient, suspects the existence of the message, a form of security through obscurity...
encoded and posted to a public bulletin board such as Usenet
Usenet
Usenet is a worldwide distributed Internet discussion system. It developed from the general purpose UUCP architecture of the same name.Duke University graduate students Tom Truscott and Jim Ellis conceived the idea in 1979 and it was established in 1980...
.
Ciphertext
Young and Yung also mentioned having the cryptotrojan unconditionally write the asymmetric ciphertextCiphertext
In cryptography, ciphertext is the result of encryption performed on plaintext using an algorithm, called a cipher. Ciphertext is also known as encrypted or encoded information because it contains a form of the original plaintext that is unreadable by a human or computer without the proper cipher...
s to the last few unused sectors of every writable disk that is inserted into the machine. The sectors remain marked as unused. This can be done using a USB
Universal Serial Bus
USB is an industry standard developed in the mid-1990s that defines the cables, connectors and protocols used in a bus for connection, communication and power supply between computers and electronic devices....
token. So, the trojan author may be one of dozens or even thousands of people who are given the stolen information. Only the trojan author can decrypt the ciphertext because only the author knows the needed private decryption key. This attack is from the field known as cryptovirology
Cryptovirology
Cryptovirology is a field that studies how to use cryptography to design powerful malicious software. The field was born with the observation that public-key cryptography can be used to break the symmetry between what an antivirus analyst sees regarding a virus and what the virus writer sees...
.
Use by police
In 2000, the FBIFederal Bureau of Investigation
The Federal Bureau of Investigation is an agency of the United States Department of Justice that serves as both a federal criminal investigative body and an internal intelligence agency . The FBI has investigative jurisdiction over violations of more than 200 categories of federal crime...
used a keystroke logger to obtain the PGP
Pretty Good Privacy
Pretty Good Privacy is a data encryption and decryption computer program that provides cryptographic privacy and authentication for data communication. PGP is often used for signing, encrypting and decrypting texts, E-mails, files, directories and whole disk partitions to increase the security...
passphrase
Passphrase
A passphrase is a sequence of words or other text used to control access to a computer system, program or data. A passphrase is similar to a password in usage, but is generally longer for added security. Passphrases are often used to control both access to, and operation of, cryptographic programs...
of Nicodemo Scarfo, Jr.
Nicodemo Scarfo, Jr.
Nicodemo Salvatore "Nicky" Scarfo Jr. is the second son of convicted Philadelphia crime family boss Nicodemo "Little Nicky" Scarfo, Sr. In his 20s, he was allegedly inducted into the Lucchese crime family sometime in the early 1990s....
, son of mob boss Nicodemo Scarfo
Nicodemo Scarfo
Nicodemo "Little Nicky" Domenico Scarfo is a member of the American Mafia who eventually became the Boss of the Philadelphia crime family after the death of Angelo Bruno and Phil Testa...
.
Also in 2000, the FBI lured two suspected Russian cyber criminals to the US in an elaborate ruse, and captured their usernames and passwords with a keylogger that was covertly installed on a machine that they used to access their computers in Russia. The FBI then used these credentials to hack into the suspects' computers in Russia in order to obtain evidence to prosecute them.
Countermeasures
The effectiveness of countermeasures varies, because keyloggers use a variety of techniques to capture data and the countermeasure needs to be effective against the particular data capture technique. For example, an on-screen keyboard will be effective against hardware keyloggers, transparency will defeat some screenloggers - but not all - and an anti-spyware application that can only disable hook-based keyloggers will be ineffective against kernel-based keyloggers.Also, keylogger software authors may be able to update the code to adapt to countermeasures that may have proven to be effective against them.
Anti keyloggers
An anti keyloggerAnti keylogger
An anti keylogger is a type of software specifically designed for the detection of keystroke logger software; often, such software will also incorporate the ability to delete or at least immobilize hidden keystroke logger software on your computer...
is a piece of software specifically designed to detect keyloggers on your computer, typically comparing all files in your computer against a database of keyloggers looking for similarities which might signal the presence of a hidden keylogger. As anti keyloggers have been designed specifically to detect keyloggers, they have the potential to be more effective than conventional anti virus software; some anti virus softwares do not consider certain keyloggers a virus, as under some circumstances a keylogger can be considered a legitimate piece of software.
Live CD/USB
Rebooting the computer using a Live CDLive CD
A live CD, live DVD, or live disc is a CD or DVD containing a bootable computer operating system. Live CDs are unique in that they have the ability to run a complete, modern operating system on a computer lacking mutable secondary storage, such as a hard disk drive...
or write-protected Live USB
Live USB
A live USB is a USB flash drive or a USB external hard disk drive containing a full operating system that can be booted. Live USBs are closely related to live CDs, but sometimes have the ability to persistently save settings and permanently install software packages back onto the USB device...
is a possible countermeasure against software keyloggers if the CD is clean of malware and the operating system contained on it is secured and fully patched so that it cannot be infected as soon as it is started. Booting a different operating system does not impact the use of a hardware or BIOS based keylogger.
Anti-spyware / Anti-virus programs
Many anti-spyware applications are able to detect some software keyloggers and quarantine, disable or cleanse them. However, because many keylogging programs are legitimate piece of software under some circumstances, anti spyware often neglects to label keylogging programs as spyware or a virus. These applications are able to detect software-based keyloggers based on patterns in executable codeSubroutine
In computer science, a subroutine is a portion of code within a larger program that performs a specific task and is relatively independent of the remaining code....
, heuristics and keylogger behaviours (such as the use of hooks
Hooking
In computer programming, the term hooking covers a range of techniques used to alter or augment the behavior of an operating system, of applications, or of other software components by intercepting function calls or messages or events passed between software components...
and certain API
Application programming interface
An application programming interface is a source code based specification intended to be used as an interface by software components to communicate with each other...
s).
No software-based anti-spyware application can be 100% effective against all keyloggers.
Also, software-based anti-spyware cannot defeat non-software keyloggers (for example, hardware keyloggers attached to keyboards will always receive keystrokes before any software-based anti-spyware application).
However, the particular technique that the anti-spyware application uses will influence its potential effectiveness against software keyloggers. As a general rule, anti-spyware applications with higher privileges
Ring (computer security)
In computer science, hierarchical protection domains, often called protection rings, are a mechanism to protect data and functionality from faults and malicious behaviour . This approach is diametrically opposite to that of capability-based security.Computer operating systems provide different...
will defeat keyloggers with lower privileges. For example, a hook-based anti-spyware application cannot defeat a kernel-based keylogger (as the keylogger will receive the keystroke messages before the anti-spyware application), but it could potentially defeat hook- and API-based keyloggers.
Network monitors
Network monitorsNetwork monitoring
The term network monitoring describes the use of a system that constantly monitors a computer network for slow or failing components and that notifies the network administrator in case of outages...
(also known as reverse-firewalls) can be used to alert the user whenever an application attempts to make a network connection. This gives the user the chance to prevent the keylogger from "phoning home
Phoning home
Phoning home, in computing, refers to an act of client to server communication where a client device or client application software reports its location on a network, the currently logged on user, or any other information to a server computer...
" with his or her typed information.
Automatic form filler programs
Automatic form-filling programs may prevent keylogging by removing the requirement for a user to type personal details and passwords using the keyboard. Form fillerForm filler
A form filler is a software program that automatically fills forms in a UI. Form fillers can be part of a larger program, like a password manager or a enterprise single sign-on solution....
s are primarily designed for web browser
Web browser
A web browser is a software application for retrieving, presenting, and traversing information resources on the World Wide Web. An information resource is identified by a Uniform Resource Identifier and may be a web page, image, video, or other piece of content...
s to fill in checkout pages and log users into their accounts. Once the user's account and credit card
Credit card
A credit card is a small plastic card issued to users as a system of payment. It allows its holder to buy goods and services based on the holder's promise to pay for these goods and services...
information has been entered into the program, it will be automatically entered into forms without ever using the keyboard or clipboard
Clipboard (software)
The clipboard is a software facility that can be used for short-term data storage and/or data transfer between documents or applications, via copy and paste operations...
, thereby reducing the possibility that private data is being recorded. However someone with physical access to the machine may still be able to install software that is able to intercept this information elsewhere in the operating system or while in transit on the network. (Transport Layer Security
Transport Layer Security
Transport Layer Security and its predecessor, Secure Sockets Layer , are cryptographic protocols that provide communication security over the Internet...
(TLS) prevents the interception of data in transit by network sniffers and proxy tools
Proxy server
In computer networks, a proxy server is a server that acts as an intermediary for requests from clients seeking resources from other servers. A client connects to the proxy server, requesting some service, such as a file, connection, web page, or other resource available from a different server...
.)
One-time passwords (OTP)
Using one-time passwordOne-time password
A one-time password is a password that is valid for only one login session or transaction. OTPs avoid a number of shortcomings that are associated with traditional passwords. The most important shortcoming that is addressed by OTPs is that, in contrast to static passwords, they are not vulnerable...
s may be keylogger-safe, as each password is invalidated as soon as it's used. This solution may be useful for someone using a public computer, however an attacker who has remote control over such a computer can simply wait for the victim to enter his/her credentials before performing unauthorised transactions on their behalf while their session is active.
One-time passwords also prevent replay attack
Replay attack
A replay attack is a form of network attack in which a valid data transmission is maliciously or fraudulently repeated or delayed. This is carried out either by the originator or by an adversary who intercepts the data and retransmits it, possibly as part of a masquerade attack by IP packet...
s where an attacker uses the old information to impersonate. One example is online banking
Online banking
Online banking allows customers to conduct financial transactions on a secure website operated by their retail or virtual bank, credit union or building society.-Features:...
where one-time passwords are implemented to protect accounts from keylogging attacks as well as replay attacks. KYPS
KYPS
KYPS is a free web-based service that enables users to log into websites, which usually require a username/password combination, using one-time passwords. The main difference between KYPS and similar password management technologies is that the password is never disclosed to the local computer...
is a service that gives OTP access to websites that normally do not offer OTP access.
Security tokens
Use of smart cardSmart card
A smart card, chip card, or integrated circuit card , is any pocket-sized card with embedded integrated circuits. A smart card or microprocessor cards contain volatile memory and microprocessor components. The card is made of plastic, generally polyvinyl chloride, but sometimes acrylonitrile...
s or other security token
Security token
A security token may be a physical device that an authorized user of computer services is given to ease authentication...
s may improve security against replay attack
Replay attack
A replay attack is a form of network attack in which a valid data transmission is maliciously or fraudulently repeated or delayed. This is carried out either by the originator or by an adversary who intercepts the data and retransmits it, possibly as part of a masquerade attack by IP packet...
s in the face of a successful keylogging attack, as accessing protected information would require both the (hardware) security token as well as the appropriate password/passphrase. Knowing the keystrokes, mouse actions, display, clipboard etc used on one computer will not subsequently help an attacker gain access to the protected resource. Some security tokens work as a type of hardware-assisted one-time password system, and others implement a cryptographic challenge-response authentication
Challenge-response authentication
In computer security, challenge-response authentication is a family of protocols in which one party presents a question and another party must provide a valid answer to be authenticated....
, which can improve security in a manner conceptually similar to one time passwords. Smartcard readers
Card reader
A card reader is a data input device that reads data from a card-shaped storage medium. Historically, paper or cardboard punched cards were used throughout the first several decades of the computer industry to store information and programs for computer system, and were read by punched card readers...
and their associated keypads for PIN
Personal identification number
A personal identification number is a secret numeric password shared between a user and a system that can be used to authenticate the user to the system. Typically, the user is required to provide a non-confidential user identifier or token and a confidential PIN to gain access to the system...
entry may be vulnerable to keystoke logging through a so called supply chain attack
Supply chain attack
A supply chain attack is a cryptographic attack where a product, typically a device that performs encryption or secure transactions, is tampered with during manufacture or while it is still in the supply chain by persons with physical access...
where an attacker substitutes the card reader/PIN entry hardware for one which records the user's PIN.
On-screen keyboards
Most on screen keyboards (such as the onscreen keyboard that comes with Windows XPWindows XP
Windows XP is an operating system produced by Microsoft for use on personal computers, including home and business desktops, laptops and media centers. First released to computer manufacturers on August 24, 2001, it is the second most popular version of Windows, based on installed user base...
) send normal keyboard event messages to the external target program to type text. Every software keylogger can log these typed characters sent from one program to another.
Additionally, keylogging software can take screenshots of what is displayed on the screen (periodically, and/or upon each mouse click), which means that although certainly a useful security measure, an on-screen keyboard will not protect from all keyloggers.
Keystroke interference software
Keystroke interference software is also available.These programs attempt to trick keyloggers by introducing random keystrokes, although this simply results in the keylogger recording more information than it needs to. An attacker has the task of extracting the keystrokes of interest—the security of this mechanism, specifically how well it stands up to cryptanalysis
Cryptanalysis
Cryptanalysis is the study of methods for obtaining the meaning of encrypted information, without access to the secret information that is normally required to do so. Typically, this involves knowing how the system works and finding a secret key...
, is unclear.
Speech recognition
Similar to on-screen keyboards, speech-to-text conversionSpeech recognition
Speech recognition converts spoken words to text. The term "voice recognition" is sometimes used to refer to recognition systems that must be trained to a particular speaker—as is the case for most desktop recognition software...
software can also be used against keyloggers, since there are no typing or mouse movements involved. The weakest point of using voice-recognition software may be how the software sends the recognized text to target software after the recognition took place.
Handwriting recognition and mouse gestures
Also, many PDAPersonal digital assistant
A personal digital assistant , also known as a palmtop computer, or personal data assistant, is a mobile device that functions as a personal information manager. Current PDAs often have the ability to connect to the Internet...
s and lately tablet PC
Tablet computer
A tablet computer, or simply tablet, is a complete mobile computer, larger than a mobile phone or personal digital assistant, integrated into a flat touch screen and primarily operated by touching the screen...
s can already convert pen (also called stylus) movements on their touchscreen
Touchscreen
A touchscreen is an electronic visual display that can detect the presence and location of a touch within the display area. The term generally refers to touching the display of the device with a finger or hand. Touchscreens can also sense other passive objects, such as a stylus...
s to computer understandable text successfully. Mouse gestures utilize this principle by using mouse movements instead of a stylus. Mouse gesture programs convert these strokes to user-definable actions, such as typing text. Similarly, graphics tablet
Graphics tablet
A graphics tablet is a computer input device that enables a user to hand-draw images and graphics, similar to the way a person draws images with a pencil and paper. These tablets may also be used to capture data or handwritten signatures...
s and light pen
Light pen
A light pen is a computer input device in the form of a light-sensitive wand used in conjunction with a computer's CRT TV set or monitor. It allows the user to point to displayed objects, or draw on the screen, in a similar way to a touch screen but with greater positional accuracy...
s can be used to input these gestures, however these are less common everyday.
The same potential weakness of speech recognition applies to this technique as well.
Macro expanders/recorders
With the help of many programs, a seemingly meaningless text can be expanded to a meaningful text and most of the time context-sensitively, e.g. "en.wikipedia.org" can be expanded when a web browser window has the focus. The biggest weakness of this technique is that these programs send their keystrokes directly to the target program. However, this can be overcome by using the 'alternating' technique described below, i.e. sending mouse clicks to non-responsive areas of the target program, sending meaningless keys, sending another mouse click to target area (e.g. password field) and switching back-and-forth.Non-technological methods
Alternating between typing the login credentials and typing characters somewhere else in the focus window can cause a keylogger to record more information than they need to, although this could easily be filtered out by an attacker. Similarly, a user can move their cursor using the mouse during typing, causing the logged keystrokes to be in the wrong order e.g. by typing a password beginning with the last letter and then using the mouse to move the cursor for each subsequent letter. Lastly, someone can also use context menuContext menu
A context menu is a menu in a graphical user interface that appears upon user interaction, such as a right mouse click or middle click mouse operation...
s to remove, cut, copy, and paste parts of the typed text without using the keyboard. An attacker who is able to capture only parts of a password will have a smaller key space
Key space
In cryptography, an algorithm's key space refers to the set of all possible keys that can be used to initialize it. For example, if an algorithm works using a key that is a string of 10 bits, then its key space is the set of all binary strings of length 10. i.e...
to attack if he chose to execute a brute-force attack.
Another very similar technique utilizes the fact that any selected text portion is replaced by the next key typed. E.g. if the password is "secret", one could type "s", then some dummy keys "asdfsd". Then these dummies could be selected with mouse, and next character from the password "e" is typed, which replaces the dummies "asdfsd".
These techniques assume incorrectly that keystroke logging software cannot directly monitor the clipboard, the selected text in a form, or take a screenshot every time a keystroke or mouse click occurs. They may however be effective against some hardware keyloggers.
See also
- Anti keyloggerAnti keyloggerAn anti keylogger is a type of software specifically designed for the detection of keystroke logger software; often, such software will also incorporate the ability to delete or at least immobilize hidden keystroke logger software on your computer...
- Black-bag cryptanalysisBlack-bag cryptanalysisIn cryptography, black-bag cryptanalysis is a euphemism for the acquisition of cryptographic secrets via burglary, or the covert installation of keystroke logging or trojan horse software/hardware on target computers or ancillary devices...
- Computer surveillanceComputer surveillanceComputer surveillance is the act of performing surveillance of computer activity, and of data stored on a hard drive or being transferred over the Internet....
- Digital footprintDigital footprintA digital footprint is a trail left by an entity's interactions in a digital environment; including their usage of TV, mobile phone, internet and world wide web, mobile web and other devices and sensors...
- Hardware keyloggerHardware keyloggerHardware keyloggers are used for keystroke logging, a method of capturing and recording computer users' keystrokes, including sensitive passwords. They can be implemented via BIOS-level firmware, or alternatively, via a device plugged inline between a computer keyboard and a computer...
- Reverse connectionReverse connectionA reverse connection is usually used to bypass firewall restrictions on open ports. A firewall usually blocks open ports,but does not block outgoing traffic...
- SpywareSpywareSpyware is a type of malware that can be installed on computers, and which collects small pieces of information about users without their knowledge. The presence of spyware is typically hidden from the user, and can be difficult to detect. Typically, spyware is secretly installed on the user's...
- Trojan horseTrojan horse (computing)A Trojan horse, or Trojan, is software that appears to perform a desirable function for the user prior to run or install, but steals information or harms the system. The term is derived from the Trojan Horse story in Greek mythology.-Malware:A destructive program that masquerades as a benign...
- Virtual keyboardVirtual keyboardA virtual keyboard is a software component that allows a user to enter characters. A virtual keyboard can usually be operated with multiple input devices, which may include a touchscreen, an actual keyboard and a computer mouse.- Types :...