WASHINGTON: Computer viruses are everywhere these days. If you connect to the Internet, it’s just a matter of time before you contract one, no matter how safe you might feel.

Few people know the telltale signs of a virus or are aware about what the different types of viruses can and cannot do. Here’s an overview — as well as some tips on what to do once you contract a virus.

In general, viruses cause computer to act in ways it normally does not. More specifically, if you find your computer freezing up while you are working on it or during startup, you could have a computer virus.

Or if your computer shuts down during your computing sessions or interrupts you with unusual error messages, a virus is probably at work. Finally, if you are unable to use certain programmes or open documents that previously worked fine, suspect a virus.

Macro viruses, among the most frequently found, infect the files of programmes that allow macros to be stored in the data files that users create. Microsoft Word and Microsoft Excel are two such programmes, and both are notorious for being frequent targets of macro viruses.

Companion viruses infect executable (.exe) files. These viruses disguise themselves with the same name as executable programmes, except they use the extension.com, which by default gets executed before.exe files. When a user goes to run, for example, myprogram.exe, myprogram.com is launched instead, initiating the virus.

The ways in which viruses can put a stop to your work are more numerous than the ways they infiltrate your computer.

“Worm” viruses created with the Visual Basic programming language are among the most common. They are usually transmitted by e-mail. Worm viruses often mail themselves to everyone in your e-mail address book and, once lodged on a computer, can do everything from popping up annoying messages to scrambling data on your hard drive until it is unusable.

Polymorphic viruses, among the most difficult to detect, change their characteristics each time they infect a computer. Thankfully, these viruses are more difficult to create and therefore found less frequently.—dpa