Signature-based detection - detects by comparing a virus signature ( a binary pattern of known viruses) against files being scanned.
Heuristic-based detection - detects behavior in and patterns of code that indicates a virus may be present. Suspicious Code is ran in a runtime virtual environment to further test for virus behavior. This can find new viruses not in the virus definitions.
Behavioural-based detection - Detects viruses when they are run based on the behavior the virus exhibits
Sandbox detection - similar to behavior based, this method Executes a potential virus in a runtime environment and monitors behavior
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