Viruses can be caught from various sources including shareware, files downloaded from the Internet, software from unknown origins, and bulletin boards.
There are four basic types of viruses:
File Infectors: These attach themselves to executable files and spread to other files when the program is run.
Boot Sector: These replace the master boot record (or boot sector on a floppy disk). They write themselves into memory any time the computer is booted.
Trojan Horses: These are disguised as legitimate programs, but when loaded, they begin to harm the system.
Macro Viruses: These common nuisances attach themselves as executable code to documents (such as Microsoft Word documents) and run when the document is opened. (They can also attach themselves to certain kinds of e-mail.) It used to be true that you couldn't get a virus from opening a document; running a program was required. Unfortunately, this has changed thanks to the widespread use of macros by computer users. While macros are very valuable, they mean that when you open a document you are running a program.
Viruses have become a way of life in the computer world. With this in mind, there are several measures you can take to prevent, or at least minimize, the damage:
Purchase a good antivirus program-there are several available. Make sure your choice is compatible with Windows 95. Old MS-DOS antivirus programs do not work well with Windows 95 and might do more damage than good.
If the computer has a BIOS setting that allows you to disable boot-sector writes (prevent applications from writing to the boot section of the hard disk), enable it! This setting must be disabled before installing Windows 95.
Viruses are often transmitted by floppy disks. Be careful when reading a floppy disk of unknown origin or using your disk on an unfamiliar machine.
Currently, many viruses and macroviruses are transmitted over the Internet. Use extreme caution when you download files, especially if they come from sources other than a manufacturer's Web site. The most secure protection against Internet-distributed viruses is to make sure you have an antivirus program running at all times (or at least when you're downloading and first running new files).
Trust no one when it comes to loading programs on your machine. Be aware that any program you load on your computer could contain a virus.
Keep your antivirus program updated. Hundreds of new viruses are written and transmitted each month.