Usually if you create malicous programs(virus,spyware…), the antivirus will detect easily. It will scan the source code. if it finds the malicious source codes, then it will alert as “virus”. To know more details about antiviru program read this article:
How does Anti Virus detects viruses
I hope you know about the antivirus functions completely. In that article, i have mentioned “Crypter” keyword. Now let us see more about Crypter.
What is Crypter?
You can make the any type of malicious programs(virus,spyware,…) undetectable by all antivirus.
How crypter makes undetectable virus?
i have told that crypter will make virus undetectable. ok. How it will do? It will encrypt the malcious code.
In “mission impossible” movie, the villaim wear mask and make heroin to believe that he is the hero.
Likewise , this crypter will create a masked form of Malicious codes. So the Antivirus programs will think that these codes are safe to use.
Drawback of Crypter
Now a days the antivirus programs upgraded to detect the malicious codes. If the crypter software is publicaly available, the antivirus get the algorithm of those crypter and include in their virus definitions. So if the virus is encrypted with that crypter, antivirus easily find that it is malicious code.
Fully Undetectable Crypter(FUD)
The crypter that is not publicaly available is known as FUD crypter. so FUD crypter will be useful to create fully undetectable virus programs.