Multiscanning

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. 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. 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.

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Wikipedia