Stump the PC Club is a free tech-advice column written by members of the North Orange County Computer Club, which has been in existence since 1976. Visit the club’s site at noccc.org.
QUESTION: Occasionally I get warning that a file is infected with a virus and I think it might not be. Is there a way to determine if it is truly infected?
PC CLUB: No anti-virus program is perfect; they either report false positives or false negatives. A false positive is when the program reports that a file is infected when it actually is not. A false negative, which is more dangerous, is when an infected file is missed. Some programs are more aggressive and, as a result, report more false positives. A good Web site for reviewing the performance of various anti-virus programs can be found at http://www.av-comparatives.org/.
If you have a file that you suspect as being infected or merely want to confirm your own anti-virus program’s results, you can submit it to a Web site for further analysis. You simply upload the suspect file to the site and it is scanned by approximately 40 different anti-virus programs. Not all of the results will be the same so some judgment on your part is required to draw a conclusion. The Web site is http://www.virustotal.com/.
Another method is to have your PC scanned by an on-line anti-virus site. An example of this is Trend Micro’s Housecall and is located at http://housecall.trendmicro.com/. The Web site will ask you to download and run a small file following which your PC will be scanned. This method will not allow you to check an individual file but will generally scan your entire PC. Even though you shouldn’t install more than one anti-virus on your PC at a time, this doesn’t actually install an additional anti-virus program and it is safe to run. You can search Google for “online antivirus” and find other sites that do this including Panda Active Scan, Kaspersky Antivirus and BitDefender.
Panda Active Scan will not allow to scan an individual file but it has an option that allows you to select a particular folder which is very convenient. Just remember that all anti-virus programs will not report the same result which is to be expected.
Ed Schwartz is a member of the North Orange County Computer Club. To send in a question, go to edwardns.com and click the Contact Me menu. Archives of previous columns are also on the website.