Short for “malicious software,” malware is a type of computer program that helps cyber attackers carry out malicious activities using your computer.

A careless download or visit to a malicious site can cause a piece of malware to be installed on your system. And it won’t take long before it starts stealing your files, deleting important data, or spying on you.

There are many types of malware, each one specializing in a specific kind of mischief.

Other interesting terms…

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what is malware

7 Most Commonly Seen Types of Malware

Knowing the different malware types can guide you in warding them off. We listed some of the most commonly seen malware kinds below.


While the term “computer virus” used to refer to malware of all kinds, that is no longer the case. Today, viruses comprise just one malware type, which multiply or copy themselves to spread from one computer to a connected device. To do that, they modify programs on an infected system. Once the infected program runs, the virus does what it’s designed to do.


Worms are probably the oldest malware. In fact, the first “virus” or what we know now as “malware” is the Creeper worm. Like viruses, a worm spreads from one computer to a connected device without human intervention. Unlike a virus, though, a worm spreads even if a user doesn’t open any program on his or her computer.


Today, Trojans have taken the place of worms as the most commonly used malware type. Trojans are hard to detect because they typically mimic legitimate programs, hence the name. But unlike worms, Trojans require an action on the part of a computer user to run. As such, hackers typically send them as email attachments that users download and install or as embedded links that take victims to malicious pages.


Ransomware are specifically designed to encrypt certain types of files on a user’s computer. They usually come with a ransom note asking victims to pay up or lose their files forever. 


While adware are not all malicious, they can certainly be annoying. Adware expose their victims to unwanted advertisements. To do that, adware redirect users’ browsers to pages that ask them to answer surveys to win prizes, for example. Little do victims know that these pages are fronts for phishing attacks.


Malvertisements work like adware. But unlike the latter, malvertisements hijack legitimate ads or ad networks to deliver malware to victims’ systems. Hackers embed malicious code into an ad. When clicked, users will be redirected to malicious websites or install malware on their computers.


Spyware are most commonly used to gain information about an individual or organization. They typically figure in phishing attacks. Typical spyware payloads include keylogging or recording every keystroke users make on infected systems. Other means to obtain confidential data include stealing browser cookies, which puts users who save passwords on their browsers at significant risk.

Today’s malware no longer sport the payload of a single type. Most combine the features of various malware types to take over victims’ computers successfully. The good news is that a lot of them can be detected by antimalware.

Regular patches to prevent vulnerability exploitation, another commonly used means to get malware onto target computers, also work. An example would be Wannacry. While it is considered a ransomware variant, it was distributed via the Eternal Blue exploit, which affects vulnerable Windows systems.