Facility Code : In card access, a portion of the identifying characteristic of an access credential that is common to a group of users in secured facility.
Fail-Safe : An electric lock that automatically unlocks with any power interruptions.
Fail-Secure : An electric lock that requires power to unlock. (Most fail secure devices are always unlocked for egress, however.)
Fire Door : A door that has been certified as a fire and smoke barrier. Special rules govern fire doors, including permissible hardware that can be installed.
Fire Door Latch : A latch that has a 3/4 inch throw and an antifriction retractor.
Form C : contact A relay or switch mechanism that contains three terminals (normally open, common, and normally closed).
Fuse A : protective device, placed in a circuit as a safeguard, that contains a metal. When the current flow becomes too great, the metal melts, thus breaking the circuit.
False Rejects : False Rejects are when an authentication system fails to recognize a valid user.
Fast File System : The first major revision to the Unix file system, providing faster read access and faster (delayed, asynchronous) write access through a disk cache and better file system layout on disk. It uses inodes (pointers) and data blocks.
Fast Flux : Protection method used by botnets consisting of a continuous and fast change of the DNS records for a domain name through different IP addresses.
Fault Line Attacks : Fault Line Attacks use weaknesses between interfaces of systems to exploit gaps in coverage.
File Transfer Protocol (FTP) : A TCP/IP protocol specifying the transfer of text or binary files across the network.
Filter : A filter is used to specify which packets will or will not be used. It can be used in sniffers to determine which packets get displayed, or by firewalls to determine which packets get blocked.
Filtering Router : An inter-network router that selectively prevents the passage of data packets according to a security policy. A filtering router may be used as a firewall or part of a firewall. A router usually receives a packet from a network and decides where to forward it on a second network. A filtering router does the same, but first decides whether the packet should be forwarded at all, according to some security policy. The policy is implemented by rules (packet filters) loaded into the router.
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 logical or physical discontinuity in a network to prevent unauthorized access to data or resources.
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.
Forest : A forest is a set of Active Directory domains that replicate their databases with each other.
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.
Form-Based Authentication :Form-Based Authentication uses forms on a webpage to ask a user to input username and password information.
Forward Lookup : Forward lookup uses an Internet domain name to find an IP address
Forward Proxy :Forward Proxies are designed to be the server through which all requests are made.
Fragment Offset :The fragment offset field tells the sender where a particular fragment falls in relation to other fragments in the original larger packet.
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.)
Full Duplex : A type of duplex communications channel which carries data in both directions at once. Refers to the transmission of data in two directions simultaneously. Communications in which both sender and receiver can send at the same time.
Fully-Qualified Domain Name : A Fully-Qualified Domain Name is a server name with a hostname followed by the full domain name.
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".