So…what is a Polymorphic Virus? Quoting the technopedia:
“A polymorphic virus is a complicated computer virus that affects data types and functions. It is a self-encrypted virus designed to avoid detection by a scanner. Upon infection, the polymorphic virus duplicates itself by creating usable, albeit slightly modified, copies of itself.” – technopedia
So, perfect. Your AV works by recognizing defined viral signatures…so the coders who created the virus know this and write code into their virus that makes it change a bit each time it replicates…just like biological viruses do.
Then, there are the worst…metamorphic viruses. Metamorphic viruses are capable of changing themselves by translating, editing and rewriting their own code, using various methods.
So, the AV software companies are seeking these viruses in the wild, and perhaps purchasing them on the dark web, to get their signatures, and the signatures of their progeny, etc.
This is an endless chase: The AV folks constantly updating their software with definitions…well, that’s the ‘blacklist’ AV software. It is a failure because of the sophistication of the malware.
Whitelisting is somewhat better: You tell the software which programs to allow to run, and no others. Unfortunately, this requires a lot of knowledge to use correctly, because incorrect use will cripple the computer and perhaps even render it inoperable.
If used well…viruses never stand a chance, since they’re not recognized to begin with so they cannot run and morph themselves to defeat AV software.
There are also “heuristic” AV programs which to some degree work on viral behavior…but they work with “pre-defined” viral behaviors, and not all viruses behave the same.
What we need is AV software with AI. Face it…you have a dog at home that barks at burglars, right? You have an immune system which recognizes ‘self’ vs. ‘not self’ and tries to kill ‘not self’. It works on its own, you don’t even know it’s there.
That’s what our computers need: An answer to polymorphic and metamorphic viruses, because to a certain degree, a metamorphic virus is AI.
Source:
http://www.thewindowsclub.com/polymorphic-virus
https://www.ukessays.com/essays/computer-science/the-protective-shield-for-polymorphic-viruses-computer-science-essay.php
https://www.blackhat.com/presentations/bh-usa-08/Hosmer/BH_US_08_Hosmer_Polymorphic_Malware.pdf