Multiscanning is running multiple anti-malware or antivirus engines concurrently. Traditionally, only a single engine can actively scan a system at a given time. Using multiple engines simultaneously can result in conflicts that lead to system freezes and application failures.^[1][2] However, a number of security applications and application suites have optimized multiple engines to work together.

Testing agencies published results showing that no single antivirus engine is 100% effective against every malware threat.^[3][4] Because each engine uses different scanning methodologies and updates their malware definition files at various frequencies, using multiple engines increases the likelihood of catching malware before it can affect a system or network.^[5]

• F-Secure – Combines an in-house engine with Avira's engine.^[6]
• G Data AntiVirus – Combines in-house and BitDefender's engines. avast has been removed with version 2014.^[7]
• HitmanPro – Combines an in-house behavioral engine with a cloud containing engines from Kaspersky Lab, BitDefender and Sophos.^{[8][circular reference]}
• Lavasoft Ad-Aware – Combines an in-house anti-spyware engine with Bitdefender's engine.
• Microsoft Forefront – Combines the engines of Authentium, Kaspersky, Norman and VirusBuster, with its own in-house engine.^[9]
• OPSWAT MetaDefender Cloud – Combines over 30 anti-malware engines to scan files for malware. Also available on-premise.^[10]
• Qihoo 360 Internet Security use Bitdefender Engine, QVM 2 Engine, 360 Cloud engine. But, the Chinese version includes the Avira engine additionally.
• TrustPort Antivirus – Combines the engines of BitDefender and AVG.
• VirusTotal

• Comparison of antivirus software
• Comparison of firewalls
• Internet Security