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
In contrast, as a general rule
, using more than one anti-spyware program like Malwarebytes' Anti-Malware, SuperAntispyware, Spybot S&D, Ad-Aware, etc will not conflict with each other or your anti-virus if using them as stand-alone scanners. In fact, doing so increases your protection coverage without
causing the same kind of conflicts or affecting the stability of your system that can occur when using more than one anti-virus. The overlap of protection from using different signature databases will aid in detection and removal of more threats when scanning your system for malware. However
, if using any of their real-time resident shields
(TeaTimer, Ad-Watch, MBAM Protection Module, Spyware Terminator Shields, etc) together at the same time, there can be conflicts
when each application tries to compete for resources and exclusive rights to perform an action. Additionally, competing tools may even provide redundant alerts which can be annoying and/or confusing.
Using two software firewalls on a single computer could cause issues with connectivity to the Internet or other unexpected behavior. Further, running multiple software firewalls can cause conflicts
that are hard to identify and troubleshoot. Only one of the firewalls can receive the packets over the network and process them. Sometimes you may even have a conflict that causes neither firewall to protect your connection. However, you can use a hardware firewall
) and a software firewall
(Kerio or ZoneAlarm) in conjunction.
A hardware firewall
is really a software firewall running on a dedicated piece of hardware or specialized device (routers, broadband gateways) that sits between a modem and a computer or network. A hardware firewall is based on "Network Address Translation
" (NAT) which hides your computer from the Internet or NAT plus "Stateful Packet Inspection
" (SPI). It can provide a strong degree of protection from most forms of attacks coming from the outside (incoming traffic
). Hardware firewalls are easy to configure and can protect every machine on a local or home network. A hardware firewall typically uses packet filtering to examine the header of a packet to determine its source and destination addresses. This information is compared to a set of predefined or user-created rules that determine whether the packet is allowed (forwarded) or denied (dropped) on particular ports. They tend to treat any kind of traffic traveling from the local network out to the Internet as safe which can be a security risk.
With a software firewall
you have customized control and can specify which applications are allowed to communicate
) over the Internet from your computer. Programs that are not explicitly allowed to do so are either blocked or else the user is prompted for confirmation before the traffic is allowed to pass. Software firewalls generally offer the best measure of protection against Trojans and worms
but they are harder to configure and must share resources with other running processes which can decrease system performance. Many software firewalls have user defined controls for setting up safe file and printer sharing and to block unsafe applications from running on your system.