What is a computer virus, trojan or adware?

A virus is computer program whose purpose is to propagate itself by traveling from file to file and from computer to computer, often destroying files in the process. Computer viruses spread by several means, including floppy and zip disks, e-mail attachments, web pages, and file-sharing. The best way to prevent viruses from infecting your computer files is to ensure that you have adequate virus-protection software installed on your computer.

A trojan is a computer program whose purpose is to leave the infected computer open for hackers to gain access and install software, look at personal files, or use the computer for illegal purposes. Some trojans are not as harmful as others, but if you do find a trojan on your computer please strongly consider backing up, formatting, and reinstalling Windows. Trojans usually infect computers through unpatched security holes in Windows and Internet Explorer.

Adware and spyware are computer programs that can do a wide range of things. Two of the main purposes are to collect data from your computer and report it back to the company, and to display popup windows of ads whether or not you are viewing websites at the time. These programs can get onto the computer any number of ways. The most common ways are as part of freeware programs such as file sharing programs, by displaying confusing dialog boxes on websites to confuse people into clicking Yes to install them, or through security holes in Internet Explorer while you browse websites.

Because of these dangers, Wellesley College provides McAfee VirusScan to protect against viruses and trojans, and McAfee AntiSpyware to protect against adware and spyware..