Hi Dw.

Is it possible to search through ".COM", ".exe" files and check if they are encrypted and so check which encryption was used in VB.NET?

sure it should be possible to figure that out. Most if not all encryption techniques leave recognisable signatures in the content they encrypt.
If you can manage to write some code that detects those patterns, you can figure out what encryption was used.
Now, in order to find out those patterns, that's the real trick. I don't know about any publicly available libraries that'd help in such a thing.

Eish. That's a problem...