6 Most Common Types of Malware and How to Recognize Them


Malware is any software intentionally designed to cause disruption to a computer, server, client, or computer network, leak private information, gain unauthorized access to information or systems, deprive users’ access to information, or unknowingly interfere with the user’s computer security and privacy.

Many types of malware exist, including computer viruses, worms, Trojan horses, ransomware, spyware, adware, rogue software, wiper, and scareware. The defense strategies against malware differ according to the type of malware but most can be thwarted by installing antivirus software, firewalls, applying regular patches to reduce zero-day attacks, securing networks from intrusion, having regular backups, and isolating infected systems. Malware is now being designed to evade antivirus software detection algorithms.

Types of Malware

These categories are not mutually exclusive, so malware may use multiple techniques. Some of the common Malware with their functions are illustrated below:


A virus is a piece of code that inserts itself into an application and executes when the app is run. A computer virus is also software usually hidden within another seemingly innocuous program that can produce copies of itself and insert them into other programs or files, and that usually performs a harmful action (such as destroying data).

A computer virus is a software that embeds itself in some other executable software (including the operating system itself) on the target system without the user’s knowledge and consent and when it is run, the virus is spread to other executable files. . Once inside a network, a virus may be used to steal sensitive data, launch DDoS attacks or conduct ransomware attacks.


A worm is stand-alone malware software that actively transmits itself over a network to infect other computers and can copy itself without infecting files. These definitions lead to the observation that a virus requires the user to run an infected software or operating system for the virus to spread, whereas a worm spreads itself. Once in place, worms can be used by malicious actors to launch DDoS attacks, steal sensitive data, or conduct ransomware attacks.

Note: The best-known types of malware, viruses and worms, are known for the manner in which they spread, rather than any specific types of behavior and have been likened to biological viruses.

3. Trojan

A Trojan horse is a harmful program that misrepresents itself to masquerade as a regular, benign program or utility in order to persuade a victim to install it. A Trojan horse usually carries a hidden destructive function that is activated when the application is started. The term is derived from the Ancient Greek story of the Trojan horse used to invade the city of Troy by stealth.

Trojan horses are generally spread by some form of social engineering, for example, where a user is duped into executing an email attachment disguised to be unsuspicious, (e.g., a routine form to be filled in), or by drive-by download. Unlike a virus or worm, Trojan malware cannot replicate itself or self-execute. It requires specific and deliberate action from the user. Like most forms of malware, Trojans are designed to damage files, redirect internet traffic, monitor the user’s activity, steal sensitive data or set up backdoor access points to the system. Trojans may delete, block, modify, leak or copy data, which can then be sold back to the user for ransom or on the dark web.

4. Adware

Adware, often called advertising-supported software by its developers, is software that generates revenue for its developer by automatically generating online advertisements in the user interface of the software or on a screen presented to the user during the installation process.

Adware typically infects devices via downloadable content – like any shareware or freeware – that opens the door to malicious third-party programs. These can covertly install ad software onto your device without your knowledge. Program developers can make money each time an ad is displayed or clicked on, meaning even legitimate companies can be tempted to include adware in their software.

The software may generate two types of revenue: one is for the display of the advertisement and another on a “pay-per-click” basis if the user clicks on the advertisement. Some advertisements also act as spyware, collecting and reporting data about the user, to be sold or used for targeted advertising or user profiling. The software may implement advertisements in a variety of ways, including a static box display, a banner display, full screen, a video, a pop-up ad, or in some other form. All forms of advertising carry health, ethical, privacy and security risks for users.

5. Remote Access

Remote access is a type of malware that controls a system through a remote network connection. While desktop sharing and remote administration have many legal uses, it connotes criminal or malicious activity. It is typically installed without the victim’s knowledge, often as a payload of a Trojan horse, and will try to hide its operation from the victim and from computer security software and other anti-virus software.

6. Exploit Kit

An exploit kit is a piece of software, a chunk of data, or a sequence of commands that takes advantage of a bug or vulnerability to cause unintended or unanticipated behavior to occur on computer software, hardware, or something electronic. Such behavior frequently includes things like gaining control of a computer system, allowing privilege escalation, or a denial-of-service (DoS or related DDoS) attack.

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