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A
	ActiveX	-	Microsoft ActiveX is a bundle of technologies that allow different applications to interact between each other in a network environment, markedly in the Internet. You can get more detailed information about this technology at  Microsoft's ActiveX Web site.
	Anti-virus software definitions (DAT files)	-	are databases of known viruses that every anti-virus program maintains. Anti-virus software manufacturers update these databases as new viruses are discovered. Generally manufacturers notify users about new viruses added to their database to let users immediately update their computers over the Internet.
B
	Back door	-	is any channel crackers can use to access your system. As a rule, it is easy for a skilled cracker to locate a back door on a computer if its software programs insufficiently protect the computer.
	BackOrifice (a.k.a. BackOrifice 2000)	-	is the name of one of the most widespread Trojan horses. If a computer is infected with BackOrifice, then attackers can get complete access to the system while it is connected to the Internet. BackOrifice lets a cracker view files, copy them, delete files, run applications on your computer remotely, even attack other systems using the infected computer.
C
	Cookie	-	is a short file from a web site written by your Web browser on your hard drive. It is used typically to save your preferences for your convenience. It is generally used to make it easier for you to find what you want. However, occasionally a cookie is used by advertisers to track user movements around the Internet.
	Cracker	-	is someone (a creep, really) who breaks into other people's computer systems often with the purpose of stealing confidential information or vandalizing the system. They are looking for a weakness in the computer's security, some channel into the system. There are more and more software and hardware tools being used in these attacks so practically any moron with basic PC skills can become a cracker.
F
	Firewall	-	is software that gives sophisticated protection of your system while it is connected to the Internet. The firewall blocks unauthorized access of your private information. It works by analyzing the routine Internet data coming into and leaving your computer.
	FTP (File Transfer Protocol)	-	is a way to upload and download files over the Internet. It lets a user view directories on a remote computer and copy or convert that computer's files.
H
	Hacker	-	is a slang term for a computer programmer. It has lately come to have the same meaning, to uninformed people, as cracker (see)
	HTTP (Hypertext Transfer Protocol)	-	is the way web pages are transmitted and received over the Internet. The web pages are supplied or served by a computer called a 'server'. These web pages are received and displayed by an HTTP client, also called a browser. HTTP is what makes the World Wide Web work.
I
	ICMP (Internet Control and Message Protocol)	-	is a way computers on the Internet send each other error and control messages. Ping software, for example, uses ICMP to determine whether a specific remote system is accessible or not.
	IP (Internet Protocol)	-	is the way data gets routed around the Internet and how it arrives at the right computer. It contains the unique Internet address of the specific computer to which the data is being sent.
J
	JavaScript	-	is a programming language designed to create interactive web pages. One of JavaScript's features is that it works practically the same on any type of computer. A JavaScript program is included within the web page and is used primarily to display data on that web page or to accept data from a form filled out by the user. It is not the same as Java, which is a much more powerful language generally used for medium to large-scale applications such as spreadsheets or accounting packages.
L
	LAN (Local Area Network)	-	is a computer network that serves users in a limited area such as a building. One local area network can be linked to another. Two or more local area networks are called a Wide Area Network (WAN).
N
	NetBus	-	second only to BackOrifice as the most prevalent Trojan horse. As with BackOrifice, NetBus, if executed on a system connected to the Internet, provides easy access to crackers. NetBus lets an attacker gain complete access to the computer to: run any application, copy, view, or delete files, manage hardware operations, etc.
P
	Port scanning	-	a cracker's attempt to find access channels and weak points in a computer's security by scanning or probing its system ports over the Internet.
	PPP (Point-to-Point Protocol)	-	a standard way of connecting computers on the Internet so data can be sent and received.
S
	SMTP (Simple Mail Transfer Protocol)	-	the most popular method used to send e-mail from one computer to another.
	Spyware	-	is any software used to obtain personal information about a user or his or her computer without informing the user or asking permission. Spyware uses an Internet connection to receive the data.
T
	TCP (Transmission Control Protocol)	-	one of the main methods of exchanging data on the Internet and together with IP is what makes the Internet work.
	Trojan horse	-	is a program that appears legitimate but does something illicit when run. It gets its name from the wooden horse the Greeks gave Troy as a "gift" because users mistake it for a useful or interesting program that they choose to download. Once installed and run, Trojans can secretly open access channels to crackers, relay passwords and credit card data or destroy user files. It's similar to a virus but generally does not replicate itself.
U
	Unix	-	is a very powerful and stable operating system primarily used on servers.
V
	Virus	-	is a program that can duplicate itself. Some don't do much except reproduce themselves, where others can cause massive damage to a system including wiping out all the files on the computer.