What Is Malware and What Can It Do?

Illustration of a digital meltdown caused by a virus infection, shown by a virus ball on a green background of ones and zeros
Carol & Mike Werner / Science Photo Library / Getty Images

Malware, a shortened combination of the words malicious and software, is a catch-all term for any sort of software designed with malicious intent. Malware is sometimes called badware and is often used synonymously with many of the common types of malware, listed below. In legal documents, malware is sometimes referred to as computer contamination so if you ever see that, it's just a fancy way of saying malware.

Malicious intent is often theft of your private information or the creation of a backdoor to your computer giving someone access to it, its resources, and its data, without your permission. However, software that does anything that it didn't tell you it was going to do could be considered malware.

Common Types of Malware?

Though some of these terms can be used to describe software with a legitimate, non-malicious intent, malware is generally understood to exist in one or more of the following forms:

  • Viruses infect program files and/or personal files.
  • Spyware collects personal information.
  • A worm is malware that can replicate and spread itself across a network.
  • A Trojan horse looks, and may even operate, as a legitimate program.
  • Browser hijacker is malware that modifies your web browser.
  • Rootkit grants administrative rights for malicious intent.
  • Malvertising is malware that uses legitimate online advertising to spread malicious software.

There are other types of programs, or parts of programs, that could be considered malicious due to the simple fact that they carry a malicious agenda, but the ones listed above are so common that they get their own categories.

Some types of adware, the term for advertisement-supported software, are considered malware but usually only when those advertisements are designed to trick users into downloading other more malicious software.

Malware Infections

Malware can infect a computer or other device in a number of ways. It usually happens completely by accident, often by downloading software that has malicious applications bundled with it.

Some malware can get on your computer by taking advantage of security vulnerabilities in your operating system and software programs. Outdated versions of browsers, and often their add-ons or plug-ins as well, are easy targets.

But most of the time malware is installed by users (that's you!) overlooking what they're doing and rushing through program installations that include malicious software. Many programs install malware-ridden toolbars, download assistants, system and internet optimizers, bogus antivirus software, and other tools by default unless you explicitly tell them not to.

Another common source of malware is from software downloads that seem at first to be safe—like a simple image, video, or audio file—but in reality is a harmful executable file that installs the malicious program.

Removing Malware

Aside from the most serious of malware infections, most are removable through some simple steps, although some are tougher to remove than others. The most common types of malware are actual programs like the legitimate software you use every day. Those programs can be uninstalled like others from Control Panel, at least in Windows operating systems.

Other malware, however, is more complex to remove, like rogue registry keys and individual files that can only be removed manually. These types of malware infections are best removed with antimalware tools and similar specialized programs. There are several, completely free, on-demand and offline virus and malware scanners that can quickly, and often painlessly, remove most types of malware.

Protecting Yourself from Malware

Obviously, the smartest way to avoid malware is to take precautions to prevent the malware from infecting your computer or device in the first place. The most important way to prevent malware from reaching your computer is by making sure you have an antivirus/antimalware program installed, and that you have it configured to constantly scan for signs of malicious activity in downloads and active files.

Beyond software that automatically keeps an eye out for malware, the most important thing you can do to protect your computer is to change your behavior. One way is to avoid opening email and attachments sent through any kind of messaging platform from people or organizations you don't know or don't trust. Even if you do know the sender, make sure that whatever is attached is something you were expecting or can follow up about in another message. One clever way malware is spread is by auto-mailing copies of itself to friends and family from an email contact list.

Also, make sure you're updating your operating system and application software whenever updates are available, especially security updates. And learn how to safely download and install software to your computer to avoid malware.