What are some difficult-to-remove viruses?

Could you mention some? Viruses that are difficult to remove by most antivirus programs.

What are some difficult-to-remove viruses?virus protection software

here's one:

http://n0d.us/67w

now GTFO you skiddie.

What are some difficult-to-remove viruses?adware

krag.exe, bar311.exe, funnyUSTscandal.exe......

those ones require some other executable programs to remove them..
You'll probably need to ask the makers of our all-too-famous thousands of virus programs technicians.

Although you probably won't get an answer because they can remove anything.

Your question is kind of hollow in that if there was a known virus and you KNEW you had a virus then there would be a program to eliminate it. Otherwise, how would you know you had one if it hadn't been discovered yet?

Maybe I don't understand what you mean by ''difficult to remove''. If it's removable----it's removable.