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Glossary of Malware Terms

ActiveX controls
A type of downloadable web browser plug-ins for Microsoft Internet Explorer providing additional interactive features to web pages. Malicious ActiveX controls pose a risk of unintended execution of malware.
Software that automatically plays, displays, or downloads advertisements to a computer.
Armored virus
A type of computer virus that takes advantage of various mechanisms specifically designed to make tracing, disassembling and reverse engineering its code more difficult.
An undocumented (and often legitimate) way of gaining access to a program, online service or an entire computer system.
A group of computers running malicious software under control of a hacker.
Buffer overflow
A technique used by certain types of malware to cause an error in a program and make it easier to run malicious code.
Companion virus
An older type of computer virus which doesn't alter files and works by creating infected companion file with the exact same name as the legitimate program, but with different file extension. The virus takes advantage of the fact that in the old MS-DOS command-line interface executables can be run by providing only the file name which facilitates the execution of infected code by an unaware user.
Computer worm
A standalone malicious computer program that replicates itself over a computer network.
Cross-site scripting
A computer security vulnerability allowing attackers to insert malicious code into a trusted website.
A rogue application designed to exploit dialup connections by making unauthorized telephone calls.
A type of Trojan designed to transfer other malware onto a PC via Internet connection.
Drive-by download
An automatic download performed without the user's consent (and often without any notice) aimed at installing malware or potentially unwanted programs.
A type of Trojan designed to install other malware files onto a PC without the need for an active Internet connection.
Executable file
A type of computer file that when opened runs a program or series of instructions contained in the file.
Computer code or command that takes advantage of software design flaws.
A category of applications which despite of not being classified as malware can worsen the performance of a computer and pose security risk.
A method employed by many computer antivirus programs designed to detect previously unknown types of malware.
An HTML tag for embedding another web document within the current HTML web page. The downside of utilizing iframes relates to the fact that they can be used for the purpose of injecting malicious code (often in the form of JavaScript applet) into an otherwise trusted page.
An application collecting information about user keyboard activity. Typically, malicious keyloggers are installed and run on a system without the user's knowledge/consent to steal logon credentials, credit card numbers, and other sensitive data.
Logic bomb
Malicious code activated by a specific event.
Macro virus
A type of computer virus that exploits the capability for creating and embedding simple scripts in popular office and cooperative applications.
Malicious app
Mobile application designed to harm user devices or personal data acting in disguise of a legitimate program.
A generic term for various types of malicious software used to disrupt computer operation, gather sensitive information, or gain access to private computer systems. The category of malware encompasses all sorts of malicious applications, including Trojan horses, most rootkits and backdoors, computer viruses, worms, spyware, keyloggers, more intrusive forms of adware, and other malicious programs.
The part of malware performing malicious action.
Phage virus
A type of computer virus that deletes or corrupts contents of the target host file instead of attaching itself to the file.
Polymorphic malware
A type of malicious software capable of changing its underlying code in order to avoid detection.
One of the ways of delivering online advertising content utilized by adware. Advertising pop-unders are usually displayed in a new browser window hidden beneath the current page and are not seen until the covering window is closed.
One of the ways of delivering online advertising content utilized by adware. Advertising pop-ups are usually displayed in a new web browser window and cover the contents of the current page.
Isolation of files and applications suspected of containing malware in order to prevent further execution and potential harm to the user's system.
Malware that restricts access to a computer system by encrypting files or locking the entire system down until the user performs requested action.
The process by which a virus makes copies of itself to carry out subsequent infections.
A computer virus that actively attacks an antivirus program in an effort to prevent detection.
A collection of software tools used by a hacker in order to mask intrusion and obtain administrator-level access to a computer or computer network.
Signature file
A file containing new malicious code patterns used by the antivirus application as a reference in the process of malware removal.
Malicious software collecting information about users without their knowledge/consent.
SQL injection
Execution of SQL commands aimed at gaining unauthorized access to an online database. This type of attack occurs when for example entry fields of web forms designed to collect information from users allow passing unchecked user input to the database. The countermeasure against this type of code injection is input validation, which limits the scope of user input that can be passed through an online form.
Trojan horse
Malicious software performing unwanted and harmful actions in disguise of a legitimate and useful program.
A computer program containing malicious segment that attaches itself to an application program or other executable component.
Windows Defender
A built-in application tool for Microsoft operating systems providing protection against viruses, spyware, and other potentially unwanted programs.
A shorthand term for cross-site scripting.
Zero-day attack
A type of attack exploiting vulnerabilities that are present in already released software but unknown to the software developer.
A computer that has been compromised by a virus or Trojan horse that puts it under the remote control of an online hijacker.

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