Using more than one anti-virus program is not advisable
. The primary concern with doing so is due to conflicts that can arise when they are running in real-time mode simultaneously
. However, even when one of them is disabled for use as a stand-alone scanner, it can affect the other. Anti-virus software components insert themselves into the operating systems core and using more than one can cause instability, crash your computer, slow performance and waste system resources
. When actively running in the background while connected to the Internet, they both may try to update their definition databases at the same time. As the programs compete for resources required to download the necessary files this often can result in sluggish system performance or unresponsive behavior.
Each anti-virus will often interpret the activity of the other as a virus and there is a greater chance of them alerting you to a "False Positive
". If one finds a virus and then the other also finds the same virus, both programs will be competing over exclusive rights on dealing with that virus. Each anti-virus will attempt to remove the offending file and quarantine it. If one finds and quarantines the file before the other one does, then you encounter the problem of both wanting to scan each other's zipped or archived files and each reporting the other's quarantined contents. This can lead to a repetitive cycle of endless alerts that continually warn you that a virus has been found when that is not the case.
Anti-virus scanners use virus definitions to check for malware and these can include a fragment of the virus code which may be recognized by other anti-virus programs as the virus itself
. Because of this, most anti-virus programs encrypt their definitions so that they do not trigger a false alarm when scanned by other security programs. Other vendors do not encrypt their definitions and they can trigger false alarms when detected by the resident anti-virus. Further, dual installation
is not always possible because most of the newer anti-virus programs will detect the presence of others and may insist they be removed prior to download and installation of another. If the installation does complete with another anti-virus already installed, you may encounter issues like system freezing, unresponsiveness
or similar symptoms while trying to use it.
To avoid these problems, use only one
anti-virus solution. Deciding which one to remove is your choice. Be aware that you may lose your subscription to that anti-virus program's virus definitions once you uninstall that software. Most anti-virus vendors recommend that you install and run only one anti-virus program at a time
When necessary, you can always get another opinion by performing an Online Virus Scan
Choosing an anti-virus is a matter of personal preference, your technical ability and experience, features offered, the amount of resources utilized, how it may affect system performance and what will work best for your system. Other factors to consider include effectiveness, user friendliness, ease of updating, ease of installation and removal. A particular anti-virus that works well for one person may not work as well for another. You may need to experiment and find the one most suitable for your use and your system. There is no universal "one size fits all" solution
that works for everyone. Another factor to consider is whether you want to use a paid for
product or free alternative
. For more specific information to consider, please read Choosing Your Anti-virus Software
Further, an anti-virus program is not enough. No single product is 100% foolproof
and can prevent, detect and remove all threats at any given time. The security community is in a constant state of change as new infections appear. Each vendor has its own definition of what constitutes malware and scanning your computer using different criteria will yield different results. The fact that each program has its own definition files means that some malware may be picked up by one that could be missed by another. Thus, a multi-layered defense using several anti-spyware products (including an effective firewall) to supplement your anti-virus combined with common sense
, safe computing
and safe surfing habits
provides the most complete protection.