Malware is unwanted software that is malicious in intent, meaning its purpose is to specifically cause harm by taking control over your computer and possibly damaging your files, such as files needed to start the computer properly. Other implications include tracking your online movements to obtain your personal electronic information, such as your bank login ID and password. Once malware has taken control, its authors can use your computer to send out spam and conduct other nefarious acts. Malware can get on your computer through various means, such as email attachments and file transfers. It can also be embedded in a Web page that you visit and download content from. Malware encompasses viruses, worms and Trojan horses -- and combinations of these.
If your computer is unusually slow or if you type in a URL and are rerouted to an unrequested website, you might have malware. The operative word is “might” since there are other possible reasons; if you’re using tons of memory and only a little is left, your system will come to a crawl, for instance. But an extremely clear indicator is a pop-up message that appears claiming you must click on it to avoid a security threat to your computer; that could be followed by your computer being hijacked. You might not be able to open anything on your desktop.
A notable characteristic of viruses is that they automatically replicate themselves. They’ll attach themselves to a file such as an email attachment. The malware author hopes that you then click on that file and release the virus or that you’ll forward the attachment to others so that even more people click on the file. That’s why viruses are said to spread. Because they copy themselves onto various files, it might be the reason if you find a stubborn file in one of your computer folders that refuses to be removed.
Worms are similar to viruses in that they make copies of themselves. Unlike viruses, worms don’t target specific files or need you to click on a file to release them. Because a worm doesn’t depend on a particular file or a host program, it is considered self-contained. The so-called “Internet crash of 1988” is one of the greatest examples of the damage a computer worm can do. The worm involved caused infected computers to freeze and servers to shut down worldwide. Worms are transmitted to your computer by exploiting vulnerabilities in applications or operating systems. A vulnerability can be a design flaw or programming error, according to “PC Magazine Fighting Spyware, Viruses, and Malware.” Worms may embed malicious code within the body of an email itself; in this case, it doesn’t require you to click on an email attachment at all.
Trojan horses are different from viruses and worms in that they don’t self-replicate; however, they are still malicious. Like worms, they are self-contained. However, they do tend to associate themselves with another type of program or file that you think is useful but actually contains dangerous code that is concealed. Thinking that it’s benign, you click on the program or file and thus invite in the Trojan horse. A Trojan horse can infect your computer with viruses and destroy files that are necessary for your computer to run properly. It may even create a so-called "back door" on your computer, which is an unauthorized access point for cybercriminals. Hackers and others with bad intentions can use the back door to gain entry to your computer and its applications and use them for their own purposes.
There’s a more complex type of malware attack that combines elements of two or more other types, and it’s appropriately known as a “blended threat” or “hybrid.” Since companies that make anti-malware software become more effective at detecting and killing malware, malware authors have to keep coming up with ways to make it harder to detect.
- PC Magazine Fighting Spyware, Viruses, and Malware; Ed Tittel
- SearchSecurity.com: Blended Threat
- Mario Tama/Getty Images News/Getty Images