Network Security Glossary of Terms

A - C

Access Control - Techniques for controlling access to sensitive files.

ActiveX - Technology developed by Microsoft that integrates local desktop programs with documents on the World Wide Web. For example, ActiveX technology allows a person to see a Word or Excel document from within the Web browser.

Anonymous Remailer - A program that removes header information from an e-mail message, making it impossible to tell where it actually came from. See SPAM.

ARP - Address Resolution Protocol.

Authenticity - Proof that the information came from the person or location that reportedly sent it. One example of authenticating software is through digital signatures.

Back Door - A deliberately planned security breach in a program. Back doors allow special access to a computer or program. Sometimes back doors can be exploited and allow a cracker unauthorized access to data.

Biometrics - Authentication techniques that utilize the analysis of a person's physical characteristics, such as fingerprints, speech, and retina scans.

BIOS - Basic Input Output System. The lowest level of the Central Processing Unit's operating system. The BIOS contains information that allows the CPU to communicate with with the computer's hardware.

Brute Force Hacking - A technique used to find passwords or encryption keys. Brute Force Hacking involves trying every possible combination of letters, numbers, etc. until the code is broken.

Bulletin Board System - A computer with bulletin board software that is dedicated to communicating with other computers. Bulletin board systems are similar to small intranets, and often have file libraries, message areas, databases, and other electronic activities.

Camping Out - Staying in a "safe" place once a hacker has broken into a system. The term can be used with a physical location, electronic reference, or an entry point for future attacks.

Cipher Text - Text that has been scrambled or encrypted so that it cannot be read without deciphering it. See Encryption

Cookie - A string of characters saved by a web browser on the user's hard disk. Many web pages send cookies to track specific user information. Cookies can be used to retain information as the user browses a web site. For example, cookies are used to 'remember' the items a shopper may have in a shopping cart.

Countermeasures - Techniques, programs, or other tools that can protect your computer against threats.

Covering Tracks - Removing evidence of one's passage.  Hackers 'cover their tracks' to prevent others from finding out how they entered a system, or to keep others form knowing that they had access to a system.

Cracker - Someone who breaks into computers. Crackers should not be confused with Hackers. The term Cracker is usually connected to computer criminals. Some of their crimes include vandalism, theft, and snooping in unauthorized areas.

Cracker Tools - Programs used to break into computers. Cracker tools are widely distributed on the Internet. They include password crackers, trojans, viruses, war-dialers, and worms.

Cracking - The act of breaking into computers. Cracking is a popular, growing subject on the Internet. Many sites are devoted to supplying crackers with programs that allow them to crack computers. Some of these programs contain dictionaries for guessing passwords. Others are used to break into phone lines (called phreaking). These sites usually display warnings like "These files are illegal, we are not responsible for what you do with them."

Cryptoanalysis - The act of analyzing (or breaking into) secure documents or systems that are protected with encryption.

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D - G

Database - A system of storing information in an organized manner.

Decryption - The act of restoring an encrypted file to its original state.

Denial of Service - Act of preventing customers, users, clients or other machines from accessing data on a computer. This is usually accomplished by interrupting or overwhelming the computer with bad or excessive information requests.

DES - Data Encryption Standard. An encryption algorythm developed by the US government.  It allows the use of variable length keys.

Digital Signature - Digital code that authenticates whomever signed the document or software. Software, messages, Email, and other electronic documents can be signed electronically so that they cannot be altered by anyone else. If someone alters a signed document, the signature is no longer valid. Digital signatures are created when someone generates a hash from a message, then encrypts and sends both the hash and the message to the intended recipient. The recipient decrypts the hash and original message, makes a new hash on the message itself, and compares the new hash with the old one. If the hashes are the same, the recipient knows that the message has not been changed..Also see software.

Encryption - The act of substituting numbers and characters in a file so that the file is unreadable until it is decrypted. Encryption is usually done using a mathematical formula which determines how the file is decrypted.

Ethernet - A common LAN (Local Area Network) communication protocol that is capable of 10MB/s data transfer rates. A newer version of Ethernet, called Fast Ethernet, is capable of 100MB/s transfer rates. The latest version, Gigabit Ethernet, supports data rates as fast as 1,000MB/s.

File Type - A group of files with the same extension (a period and three characters at the end of a filename).

Firewall - A logical "wall" around a LAN or WAN that restricts access into and out of the network.  See Gateway

Frame Relay - A communications protocol for WANs that supports fast connection speeds.

Freeware - Software available without charge. Also see Shareware.

FTP - File Transfer Protocol.

Gateway - A way to control access to networks through a firewall. Gateways also allow different types of systems to communicate with each other.

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H - O

Hacker - Person with a strong interest in computers who enjoys learning and experimenting with them. Hackers are usually very talented, smart people who understand computers better than others. The term is often confused with cracker which defines someone who breaks into computers.

Hash - A special number generated from a string of text.  Hashes are commonly used in large databases, where searching the database for a number would be faster than searching for a longer string of text.  Hashes are also used to create digital signatures.

Header - A small part of a file or message that defines certain properties. File headers include the file size, date last modified, date created, etc.  Message headers contain information on who sent it, when and from where they sent it, the name and address of the recipient, attachment information, etc.

HTML - HyperText Markup Language. This is the language of the World Wide Web. It contains hidden tags that tell the Web browser what to do. These hidden tags create all the formatting on a Web page, and they contain the information needed to jump to another place when the user clicks a link. The World Wide Web Consortium develops and maintains the HTML standards that most browsers use today.

HTTP - HyperText Transfer Protocol.

ICMP - Internet Control Message Protocol.

IDEA - International Data Encryption Algorythm. An encryption algorythm that uses a 128-bit key.

Integrity - Proof that the data is the same as originally intended. Unauthorized software or people have not altered the original information.

Internet Worm - See Worm.

Intruder - Person or software interested in breaking computer security to access, modify, or damage data. Also see Cracker, and Elite.

IP - Internet Protocol.

IP Address - An address number that is allocated to a specific computer on a network. IP Addresses consist of a series of 4 numbers between 1 and 255 and seperated by periods (.). For example, a valid IP Address could look like this: 11.35.230.42 .

ISDN - Integrated Services Digital Network. ISDN is a communications standard for sending data over digital phone lines.  Residential ISDN lines do not require modes for transferring data.When setting up ISDN, phone companies typically offer 2 lines, both capable of 64 Kbps transfer rates. These lines can be used as voice or data lines, allowing the user to talk on the phone while on the Internet, or even acquire download speeds of 128 Kbps.   Today's fastest modems are capable of only 56 Kbps transfer rates.

ISO - International Standards Orgainzation.  Organization established for defining internet protocol standards.

ISP - Internet Service Provider. This is the individual or company that provides access to the Internet for others. ISPs usually maintain a large network of modems, servers and routers. Their network is generally connected to the Internet with a high-speed connection. Clients can dial into the ISP's server through a modem or other connection to access the Internet without having to maintain a large network themselves.

Java - Programming language developed by Sunsoft Systems. This language received a lot of attention on the Internet because of its ability to run the same program on mutiple computer platforms (PC, Macintosh, UNIX, etc.).

Joyriding - Hacking into an ISP or phone service in order to get useage from that service without paying for it.

Key Pair - See Public-Key Encryption

LANs - Local Area Network. Two or more computers connected to each other.  LANs allow communication between local computers and printers. They can be linked to WANs, MANs, and the Internet.

Linux - A version of the UNIX operating system designed to run on IBM Compatible computers.

Logic Bomb - A virus that only activates itself when certain conditions are met. Logic bombs usually damage files or cause other serious problems when they are activated.

MAN - Municipal Area Network. These networks are a cross between a WAN and a LAN. They typically provide Internet access to designated communities, but are also used for local businesses that communicate across town.

Name Resolution - The allocation of an IP address to a host name. See DNS

NetBIOS - Network Basic Input / Output System. NetBIOS is an extension of the DOS BIOS that enables a PC to connect to and communicate with a LAN.

NAT - Network Address Translation. An Internet standard that enables LAN, WAN, and MAN networks to use extended IP addresses for internal use by adding an extra number to the IP address. This standard translates internal IP addresses into external IP addresses and vice versa. In doing so, it generates a type of firewall by hiding internal IP addresses.

NFS - Network File System. This operating system allows file sharing between networked computers.

NNTP - Network News Transfer Protocol. A protocol for distributing news messages over the Internet. This protocol is similar to the HTTP (Hyper Text Transfer Protocol) system.

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P - R

Packet - A block of information that is sent from one computer to another, usually over a modem, network, or the Internet.

Packet Filter - A filter used in firewalls that scans packets and decides whether to let them through.

Password Cracker - A program that uses a dictionary of words, phrases, names, etc. to guess a password.

Password encryption - A system of encrypting electronic files using a single key or password. Anyone who knows the password can decrypt the file.

Password Shadowing - The storage of a user's username and password in a network administrator database.

Penetration - Gaining access to computers or networks by bypassing security programs and passwords.

Phreaking - Breaking into phone or other communication systems. Phreaking sites on the Internet are popular among crackers and other criminals.

Ping Attack - An attack that slows down the network until it is unuseable. The attacker sends a "ping" command to the network repeatedly to slow it down. See also Denial of Service.

<Pirate - Someone who steals or distributes software without paying the legitimate owner for it. This category of computer criminal includes several different types of illegal activities: