Using anti-virus and anti-spyware software is an important part of cyber
security. But in an attempt to protect yourself, you may unintentionally
Isn't it better to have more protection?
Spyware and viruses can interfere with your computer's ability to process
information or can modify or destroy data. You may feel that the more
anti-virus and anti-spyware programs you install on your computer, the safer
you will be. It is true that not all programs are equally effective, and
they will not all detect the same malicious code. However, by installing
multiple programs in an attempt to catch everything, you may introduce
How can anti-virus or anti-spyware software cause problems?
It is important to use anti-virus and anti-spyware software (see
Understanding Anti-Virus Software and Recognizing and Avoiding Spyware for
more information). But too much or the wrong kind can affect the performance
of your computer and the effectiveness of the software itself.
Scanning your computer for viruses and spyware uses some of the available
memory on your computer. If you have multiple programs trying to scan at the
same time, you may limit the amount of resources left to perform your tasks.
Essentially, you have created a denial of service against yourself (see
Understanding Denial-of-Service Attacks for more information). It is also
possible that in the process of scanning for viruses and spyware, anti-virus
or anti-spyware software may misinterpret the virus definitions of other
programs. Instead of recognizing them as definitions, the software may
interpret the definitions as actual malicious code. Not only could this
result in false positives for the presence of viruses or spyware, but the
anti-virus or anti-spyware software may actually quarantine or delete the
How can you avoid these problems?
- Investigate your options in advance - Research available anti-virus and
anti-spyware software to determine the best choice for you. Consider the
amount of malicious code the software recognizes, and try to find out
how frequently the virus definitions are updated. Also check for known
compatibility issues with other software you may be running on your
- Limit the number of programs you install - Many vendors are now
releasing packages that incorporate both anti-virus and anti-spyware
capabilities together. However, if you decide to choose separate
programs, you really only need one anti-virus program and one
anti-spyware program. If you install more, you increase your risk for
- Install the software in phases - Install the anti-virus software first
and test it for a few days before installing anti-spyware software. If
problems develop, you have a better chance at isolating the source and
then determining if it is an issue with the software itself or with
- Watch for problems - If your computer starts processing requests more
slowly, you are seeing error messages when updating your virus
definitions, your software does not seem to be recognizing malicious
code, or other issues develop that cannot be easily explained, check
your anti-virus and anti-spyware software.
Authors: Mindi McDowell, Matt Lytle
The above article is reproduced with the kind permission of US-CERT (United States Computer Emergency Readiness Team) and the original document may be viewed by clicking here