Short for Internet Connection Firewall, a feature of the Windows XP operating system. The ICF is a firewall that protects a home or small business network that is connected to the Internet via a cable, DSL or dial-up modem. Devices that are connected to the Internet via a software or hardware router cannot use ICF.
Windows XP keeps a log of any information a user requests from the Internet -- for example, when the user requests a Web page or accesses an e-mail account. When information enters a computer, ICF checks the log to determine if it is something the user has requested. If ICF does not recognize the request, it drops the transmission and records the activity in a separate log that the user can check to see if any security issues need to be addressed.
ICF only blocks undesirable Internet traffic from coming into a network; it does not prevent outgoing traffic from being subjected to malicious hacker attacks such as Trojan horses or spyware programs.
ICF should not be used in virtual private networks because it will interfere with file sharing and print spooling.