In this educational video you will learn about the different types of viruses and how the process of infection occurs for each.
Folks at the MalwareAnalysisForHedgehogs channel often make these types of explanation video so that more people join the workforce against the sea of malware that's bombarding the internet 24/7.
One of the focal points of this video is the difference between unencrypted and encrypted viruses and how anti-virus software are being able to recognize them. For example, for unecrypted viruses, the anti-virus creates a signature from within the virus body, while for the encrypted types, the AV creates a signature from within the decrypter part of the virus.
Now, all that is for simple viruses. When it comes to more advanced types of viruses such oligomorphic or metamorphic, things get more complicated. See the full video for the complete explanation.
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Cristi Vlad Self-Experimenter and Author