Leap to a definition:
Adware - Executable
Hybrid virus - Keylogger
Malware - Probe
Rootkit - Worm
Adware
A software application in which advertising banners are displayed while the program is running; sometimes, also tracks user information, which makes it also spyware.
Ask the experts: My adware is delaying reboots.
Antivirus software
A class of program that searches your hard drive and floppy disks for any known or potential viruses.
ITKnowledge Exchange: Antivirus programs -- which one do you prefer?
Back door
A means of access to a computer system that bypasses security mechanisms, installed sometimes by an authorized person, sometimes by an attacker.
Tip: How attackers install backdoors and what to do about it
Bot
A bot (short for "robot") is a program that operates as an agent for a user or another program or simulates a human activity. On the Internet, the most ubiquitous bots are the programs, also called spiders or crawlers, that access Web sites and gather their content for search engine indexes.
Tip: Invasion of the bots
Browser hijacker
Programming that alters your browser settings so that you are redirected to Web sites you had no intention of visiting.
Learning guide: Web Browser Security
Buffer overflow
Type of attack that sends more data than a buffer was intended to hold; surplus data will overflow into adjacent buffers, corrupting or overwriting the valid data held in them or may. Data sent may include malicious code.
Tip: How buffer overflow attacks work
Data miner
In a malware context, a program that tracks and processes data about the user's browsing behavior for marketing purposes.
Denial of service (DoS)
An incident in which a user or organization is deprived of the services of a resource they would normally expect to have.
Article: New security hole in Firefox
Directory harvest attack
An attempt to determine the valid e-mail addresses associated with an e-mail server so that they can be added to a spam database.
Expert response: Deflecting e-mail spoofing
Distributed denial-of-service attack
One in which a multitude of compromised systems attack a single target, thereby causing denial of service for users of the targeted system.
Expert response: How do I find a program that activates only when the system goes into hibernation?
Email virus
Malicious computer code sent to you as an e-mail note attachment. The best two defenses against e-mail viruses for the individual user are (1) a policy of never opening an e-mail attachment (even from someone you know) unless you have been expecting the attachment and know what it contains, and (2) installing and using anti-virus software to scan any attachment before you open it.
Security school: Email security
Ethical worm
Program used to automate network-based distribution of security patches.
Tip: Ethical worms: A bad idea
Executable
Type of file containing a program that will start it to run; viruses are often sent in executable files that will run when the user opens the file.
Expert response: Virus causing your computer to reboot?
Hybrid virus
A virus that combines characteristics of more than one type of virus to infect both program files and system sectors. The virus may attack at either level and proceed to infect the other once it has established itself.
Learning guide: Malware
Hybrid virus/worm
Malicious code that combines characteristics of both those types of malware, typically featuring the virus' ability to alter program code with the worm's ability to reside in live memory and to propagate without any action on the part of the user.
Tip: Eight steps to prevent malware outbreaks
IM worm
Self-replicating malicious code that spreads in instant messaging networks.
Expert response: Scanning and removing worms received via IM messaging
In the wild
Malicious computer code that spreads in the real world as a result of normal day-to-day operations.
Keylogger
Type of spyware program that records the user's keystrokes invisibly and either transmits them to the attacker on an ongoing basis or saves them to a
secret file in the user's computer to be sent at a later time.
Tip: Keylogger basics
Malware
Programming or files developed for the purpose of doing harm.
Tip: Malware removal: Four simple steps
Macro virus
Virus that infects a word processing application and causes a sequence of actions to be performed automatically when the application is started or something else triggers it. Macro viruses tend to be surprising but relatively harmless.
Tip: Securing your Office
Password cracker
Program used to identify an unknown or forgotten password, often used by a human cracker to obtain unauthorized access.
Step-by-step guide: BIOS password hacking
Patch
Quick-repair job for a piece of programming, often as a result of some discovered vulnerability.
Toolbox: Patch Management
Patch management
Area of systems management that involves acquiring, testing, and installing multiple patches to an administered computer system.
Learning guide: Patch management
Payload
The eventual effect of a software virus.
Port scan
Series of messages sent by someone attempting to break into a computer to learn which computer network services, each associated with a "well-known" port number, the computer provides.
ITKnowledge exchange: Local LAN Vulnerabilities and Open Ports NAT
Probe
An attempt to gain access to a computer and its files through a known or probable weak point in the computer system.
Expert response: Troubleshooting a Trojan rootkit
Rootkit
A collection of tools (programs) that enable administrator-level access to a computer or computer network. It allows an attacker to mask intrusion and gain root or privileged access to the computer and, possibly, other machines on the network.
Expert advice collection: Rootkit education
Script kiddy
Derogatory term used to describe immature and unskilled -- but unfortunately still dangerous -- malware creators.
Social engineering
A non-technical kind of intrusion that relies heavily on human interaction and often involves tricking other people to break normal security procedures.
Tip: Online scams: Top 5 best of the worst
Spam
Unsolicited e-mail on the Internet
Learning center: Windows scam crackdown
Spyware
Programming that is put in someone's computer to secretly gather information about the user and relay it to advertisers or other interested parties.
Expert response: Is all spyware dangerous?
Stealth
Refers to an event, object or file that evades methodical attempts to find it.
Clinic: Rooting out a rootkit:
Stealth virus
A virus that includes mechanisms that enable it to hide from anti-virus programs.
Trojan horse
A virus in which malicious or harmful code is contained inside apparently harmless programming or data.
Tip: Spear phishing: Don't be a target
Virus
A piece of programming code usually disguised as something else that causes some unexpected and usually undesirable event. A virus is often designed so that it is automatically spread to other computer users. Generally, there are three main classes of viruses: file infectors, system or boot infectors, and macro viruses.
Expert response: The difference between antivirus and antispyware/malware software
Virus hoax
A false warning about a computer virus. Virus hoaxes are usually forwarded using distribution lists and will typically suggest that the recipient forward the note to other distribution lists. If you get a message about a new virus, you can check it out by going to one of several Web sites that keep up with viruses and virus hoaxes.
Tip: Hoaxes: Nearly as deadly as a virus
Worm
Self-replicating virus that does not alter files but resides in active memory and duplicates itself. Worms use parts of an operating system that are automatic and usually invisible to the user. It is common for worms to be noticed only when their uncontrolled replication consumes system resources, slowing or halting other tasks.
Expert response: Displaying hidden windows
This was first published in August 2006
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