User guide

Reference Guide 143
graphical user interface (GUI)
The visual representation on a computer screen that allows users
to view, enter, or change information.
hack
To use a computer or network to perform illegal acts or gain
unauthorized access.
hacker
An individual who uses a computer or network to perform illegal
acts or gain unauthorized access. The term also can refer to an
individual who is simply a computer enthusiast or expert;
however, WatchGuard publications use the former definition.
hash code
A unique, mathematical summary of a document that serves to
identify the document and its contents. Any change in the hash
code indicates that the document’s contents have been altered.
header
A series of bytes at the beginning of a communication packet that
provide identification information about the packet such as its
computer of origin, the intended recipient, packet size, and
destination port number.
Help system
A form of online information about a software or hardware
system.
hexadecimal
A numbering system containing 16 sequential numbers as base
units before adding a new position for the next number.
Hexadecimal uses the numbers 0—9 and the letters A—F.
hierarchical trust
A graded series of entities that distribute trust in an organized
fashion, commonly used in ANSI X.509 to issue certifying
authorities.
High Availability
A WatchGuard Firebox System option that enables the installation
of two Fireboxes on one network in a failover configuration. At