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
and issues with Windows resource management. 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 may interpret the activity of the other as malicious behavior and there is a greater chance of them alerting you to a "False Positive
". If one finds a virus or a suspicious file and then the other also finds the same, both programs will be competing over exclusive rights on dealing with that virus or suspicious file. Each anti-virus may attempt to remove the offending file and quarantine it at the same time resulting in a resource management issue as to which program gets permission to act first. If one anit-virus 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, keep in mind that 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. Nonetheless, 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. 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