Malware, or malicious software, is a class of software that includes any application that intentionally performs activities against the wishes of a computer user or without the user's knowledge and approval.
The term malware covers a broad and diverse group of malicious software designed to infect a computer system and perform some sort of malicious activity such as damaging and deleting files, stealing information, or providing a backdoor to allow unauthorized access and control of the computer by another person over the Internet. Some forms of malware are designed simply to create havoc, while others are more strategic and are used to add an infected computer to a botnet, to steal sensitive information, to hold a computer hostage and demand payment, or to serve up revenue-generating unsolicited advertisements.
Frequently Asked Questions
What are the most common types of malware?
- Viruses: The most well-known type of malware, viruses typically hitchhike onto a system attached to a legitimate file, and then proceed to wreak havoc by deleting and corrupting files.
- Worms: Worms exploit a network vulnerability to gain access to a computer, replicate themselves, and automatically send themselves to other network users. Once they've infected a computer system, worms typically cause hard drive damage by overwriting and deleting legitimate files.
- Trojan horses: Malware disguised as a legitimate useful file is called a Trojan horse. If an unsuspecting user opens or executes the Trojan horse file, in most cases a backdoor will be installed on the computer allowing unauthorized access by hackers who will typically use the infected machine as part of a botnet.
- Rootkits: Rootkits are a type of program that may or may not be malware, but that gains administrative control over the system. This means that rootkits have virtually unlimited power over a computer system, and since they have administrative control they are largely undetectable by malware-removal and anti-virus applications. Since rootkits have to be manually executed and installed, to avoid rootkits only ever install reputable software, and keep your operating system updated.
- Adware: Applications such as browser add-ons and toolbars that keep an eye on your internet activity and present ads in the browser are called adware.
- Spyware: This broad category of malware includes keystroke loggers and other forms of malware that watch the activity that takes place on a computer and report what they find back to someone who has something to gain by using the information.
- Ransomware: A type of scareware, ransomware takes a part or all of a computer hostage and demands payment. Once payment is received in most cases the computer remains unusable.
How does malware get onto a computer?
Different types of malware infect computer systems in different ways. In most cases, malware infections can be traced back to infected email attachments, infected software downloads, or access of questionable websites while using a vulnerable browser. This means that the best way to avoid malware is to only ever download attachments you are expecting and are confident are legitimate, download software from legitimate reputable sources, and practice safe browsing.