Fault Line Attacks - Fault Line Attacks use weaknesses between interfaces of systems to exploit gaps in coverage.
Finger - A protocol to lookup user information on a given host. A Unix program that takes an e-mail address as input and returns information about the user who owns that e-mail address. On some systems, finger only reports whether the user is currently logged on. Other systems return additional information, such as the user's full name, address, and telephone number. Of course, the user must first enter this information into the system. Many e-mail programs now have a finger utility built into them.
Fingerprinting - Sending strange packets to a system in order to gauge how it responds to determine the operating system.
Firewall - A part of a computer system or network designed to block unauthorized access while permitting authorized communications.
Flaming - Hostile and insulting behavior between Internet users.
Flooding - An attack that attempts to cause a failure in (especially, in the security of) a computer system or other data processing entity by providing more input than the entity can process properly.
Fork Bomb - A Fork Bomb works by using the fork() call to create a new process which is a copy of the original. By doing this repeatedly, all available processes on the machine can be taken up.
Fragment Overlap Attack - A TCP/IP Fragmentation Attack that is possible because IP allows packets to be broken down into fragments for more efficient transport across various media. The TCP packet (and its header) are carried in the IP packet. In this attack the second fragment contains incorrect offset. When packet is reconstructed, the port number will be overwritten.
Fragmentation - The process of storing a data file in several "chunks" or fragments rather than in a single contiguous sequence of bits in one place on the storage medium.
Frames - Data that is transmitted between network points as a unit complete with addressing and necessary protocol control information. A frame is usually transmitted serial bit by bit and contains a header field and a trailer field that "frame" the data. (Some control frames contain no data.)
Freeware - Software distributed with no charge, usually via the Internet.
Fuzzing - The use of special regression testing tools to generate out-of-spec input for an application in order to find security vulnerabilities. Also see "regression testing".