A worm is a computer program that can replicate and send copies of itself to other computers in a network. Worms are considered a subset of viruses, but unlike viruses they can travel without any human action.
For instance, the infamous Storm worm, which appeared in 2007, is thought to have infected millions of machines. It took advantage of a security hole in Windows operating systems, and added infected computers to a network of remotely controlled machines that could be used for nefarious purposes.
Like Storm, most worms are designed to exploit known security holes in software, although some propagate by tricking Internet users. Mass-mailing worms, for instance, spread via email or instant message (IM). They arrive in message attachments and once you download them the worm silently infects your machine.
Peer-to-peer (P2P) networks are another avenue for worms: cybercriminals upload infected files with desirable names to entice users into downloading them.
Once your machine is infected, the worm can corrupt files, steal sensitive information, install a backdoor giving cybercriminals access to your computer, or modify system settings to make your machine more vulnerable. They can also degrade your Internet connection and overall system performance.
The good news is there are steps you can take to keep your computer from being infected:
- Use comprehensive security software, like McAfee Total Protection™ software, and keep it up-to-date.
- If you are a Windows user, enable Windows Update to automatically apply security updates and patches.
- Use a software firewall to block unauthorized traffic to and from your computer, such as the firewall available in McAfee Total Protection software.
- Since some worms now have a phishing component—meaning that they try to trick users into running the malicious code—do not click on links in unexpected emails and IMs, or download attachments connected to them.
- Do not download or open any files on P2P sites.
If you fear that your machine is already infected, immediately run an antivirus scan. Also you can search the Internet for removal instructions on how to delete infected files manually.
Of course, given the fast-moving nature of Internet worms, your best bet is to be cautious and take steps to avoid getting infected in the first place.