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Glossary 135
email (electronic
mail)
A method of exchanging messages and files with
other people via computer networks. A popular
protocol for sending email is SMTP (Simple Mail
Transfer Protocol). Popular protocols for receiving
email are POP3 (Post Office Protocol 3) and IMAP4
(Internet Message Access Protocol 4). Web-based
email services use HTTP (Hypertext Transfer
Protocol) for sending and receiving email.
finger
A command in some operating systems that
requests network user account information.
firewall
A security system that uses rules to block or allow
connections and data transmissions between your
computer and the Internet.
firewall rule
A set of parameters that specifies a type of data
packet or network communication and an action to
perform (permit it or block it) when it is found.
fragment
An IP packet that has been split into two or more
parts, or fragments. When the size of an IP packet
exceeds the maximum frame size of a network
that it crosses, the packet must be divided into
smaller packets, or fragments.
hacker
A person who attempts unauthorized access of
other people’s computers for the purpose of
obtaining information from, or doing damage to,
those computers.
HTML (Hypertext
Markup Language)
A standard language for documents on the World
Wide Web. Codes inserted in a text file instruct
the Web browser on how to display a Web page’s
words and images for the user, and define
hypertext links between documents.
inbound
communication
An attempt by an external computer to open a
connection to your computer. The connection can
be used to send data to and from your computer.
IP (Internet Protocol)
The essential protocol by which data is sent from
one computer to another on the Internet. IP routes
packets to the appropriate destinations.