How To Tell When You Have a Computer Virus
Here are some of tell-tale signs that your computer may exhibit if it's infected by a virus.
Changes in the length of programs
Changes in the file date or time stamp
Longer program load times
Slower system operation
Reduced memory or disk space
Bad sectors on your floppy
Unusual error messages
Unusual screen activity
Failed program execution
Failed system bootups when booting ,or accidentally booting, from the A: drive.
Unexpected writes to a drive.
These symptoms don't guarantee that a virus is present; there are many other possibilities that can cause them. To determine if it's a virus follow these steps recommended by Burrell:
1. Get the most recent version of a quality anti-virus program on a computer that's behaving normally; install it on a clean floppy and write protect the diskette. Boot the suspect computer with a clean bootable diskette and run the anti-virus program from the newly created disk. If the program gives you the option to use heuristics, enable them only after the initial scan finds nothing and then scan again. (But don't turn on heuristics during the first scan, because they will increase the probability of false alarms.)
2. If nothing shows up, consider contacting the support center of the anti-virus program for further direction.
3. If still no luck, consider using these Internet newsgroups: comp.virus and alt.comp.virus. The former is better (it's moderated, for one thing); the latter (unmoderated) sometimes contains bad advice, so make sure to wait for corroboration of any suggestions received there. The gurus shoot down bad suggestions, but they can't do that before the ill-founded suggestions appear, of course.
Found a virus? Most of the experts we consulted said not to rely on the anti-virus to clean the infected file. Instead, replace it with the original clean version.
Some of the material in this article comes from Wolfgang Stiller the developer of Integrity Master anti-virus program and Nick FitzGerald editor of Virus Bulletin. More information about viruses,virus news, anti-virus software, and information how to protect your PC can be found at their web sites: http://www.stiller.com orhttp://www.virusbtn.com, along with Burrell's noted above.