A computer virus is a small software program that can spread from one computer system to another and cause interferences with computer operations. A computer virus has the capacity to corrupt or to delete data on your computer and it can use an e-mail program to spread the virus to other email addresses in your online address book. In the worst case scenario, it can even delete everything on your hard disk.
Forms of Computer Viruses
In the same way as viruses harm peoples' bodies, computer viruses can do considerable damage to computer systems. Viruses are infections. Computer infections can come in several forms and your computer can "catch" one in several ways:
- An email virus is one type of computer virus. An email virus can travel through attachments in email messages and can automatically replicate itself by mailing itself to dozens or even hundreds of people on your list of contacts found in your online address book. There are email viruses that can launch themselves into your computer while you are simply viewing the messasge. You don’t even need to double-click the message in order for the message to install itself.
- A Trojan horse is not a virus. It is a computer program that claims to be a game but, in actuality, will just do damage once you run it. It may even erase your hard disk. It cannot automatically replicate itself.
- A worm is a type of software called mallware that uses security holes and computer networks in order to replicate itself. The worm will scan the network for machines which carry a particular security hole. It will then copy itself to the machine through the security hole and will start replicating itself.
Viruses in general, start working and spreading once you start using the application or program to which the virus is attached. For instance, a program that has a virus in it will place the virus in the system’s memory each time that program is run.
Once the virus is in the memory, one of several things can happen. First, it can be programmed to attach itself to other programs and applications, folders, or disks. Second, if given the chance, it can infect a network.
How Computer Viruses Are Activated
Computer viruses are easily spread through the use of attachments in various email messages or via messages from instant messaging; so, you must never open unexpected email attachments unless you know and trust whoever sent the message.
Be very careful as computer viruses can be easily disguised as ordinary-looking attachments or even as attractive images, funny graphics, cards, video, and audio files. Computer viruses can also spread through downloads you do while online. They can be hidden in software, especially in pirated items, or in other programs and files which you are downloading.
How Computer Viruses Operate
Viruses operate in a multitude of ways. Some will stay active only when the application to which it is attached is running. Others will be inactive once the computer is turned off, while some will run every time you turn your computer on after it has infected the network or system files.
There are some indicators that will tell you that your computer is infected:
- Your computer is running slower than normal
- Computer applications are not working right
- Disk drivers and disks have become inaccessible
- You cannot print
- You find unusual, error messages
- Dialog boxes and menus are distorted
- You find double extensions on attachments which you’ve recently opened (ex. gif, jpg, vbs)
- Your antivirus program is suddenly disabled or cannot be restarted
- Antivirus programs cannot be installed in your computer or cannot run
- New and unusual icons suddenly appear on your desktop
- Strange music or sounds suddenly play from the speakers
- A program you typically use suddenly disappears from your computer without you purposely removing it
To safeguard your files and to protect your computer, take time to understand computer viruses and what you should avoid doing to save your system from the virus. Be sure to always turn on the firewall, keep your computer’s operating system updated, update your antivirus software, and use updated antispyware programs.
(plural computer viruses or computer virii)
- (computing) A program which can covertly transmit itself between computers via networks (especially the Internet) or removable storage such as CDs, USB drives, floppy disks, etc., often causing damage to systems and data.
- The term computer virus is often used instead of just virus to specify that a virus in the computing sense, rather than the biological sense, is being referred to.
- See also the note on the plural at virus.