Norton Personal Firewall, developed by Symantec

Symantec

Symantec Corporation is the largest maker of security software for computers. The company is headquartered in Mountain View, California, and is a Fortune 500 company and a member of the S&P 500 stock market index.-History:...

, is a discontinued personal firewall

Personal firewall

A personal firewall is an application which controls network traffic to and from a computer, permitting or denying communications based on a security policy. Typically it works as an application layer firewall....

 with ad blocking, program control and privacy protection capabilities.

Norton Personal Firewall program control module is able to allow or deny individual applications access to the Internet. Programs are automatically allowed or denied Internet access by Norton Personal Firewall. It uses a blacklist

Blacklist

A blacklist is a list or register of entities who, for one reason or another, are being denied a particular privilege, service, mobility, access or recognition. As a verb, to blacklist can mean to deny someone work in a particular field, or to ostracize a person from a certain social circle...

 and a whitelist to determine if the program should be allowed Internet access.

The advertisement-blocking feature of this software rewrites the HTML

HTML

HyperText Markup Language is the predominant markup language for web pages. HTML elements are the basic building-blocks of webpages....

 that one's browser uses to display Web page

Web page

A web page or webpage is a document or information resource that is suitable for the World Wide Web and can be accessed through a web browser and displayed on a monitor or mobile device. This information is usually in HTML or XHTML format, and may provide navigation to other web pages via hypertext...

s. It searches for code related to advertisements against a blacklist and prevents the web page from being displayed. When this happens, there is no notification from Norton Personal Firewall.

The Privacy Control component blocks browser cookies and active content, and prevents the transmission of sensitive data through standard POP3 e-mail clients, Microsoft Office

Microsoft Office

Microsoft Office is a non-free commercial office suite of inter-related desktop applications, servers and services for the Microsoft Windows and Mac OS X operating systems, introduced by Microsoft in August 1, 1989. Initially a marketing term for a bundled set of applications, the first version of...

 e-mail attachments and Instant Messaging

Instant messaging

Instant Messaging is a form of real-time direct text-based chatting communication in push mode between two or more people using personal computers or other devices, along with shared clients. The user's text is conveyed over a network, such as the Internet...

 services such as MSN Messenger, Windows Messenger

Windows Messenger

Windows Messenger is a client by Microsoft that is included in the Windows XP operating system. Designed for use by corporate users as well as home users, it was originally created as a streamlined and integrated version of MSN Messenger...

 and AOL Instant Messenger

AOL Instant Messenger

AOL Instant Messenger is an instant messaging and presence computer program which uses the proprietary OSCAR instant messaging protocol and the TOC protocol to allow registered users to communicate in real time. It was released by AOL in May 1997...

without the user's consent.