Lingon trainers..

[EMPiRE]

I understand that it is hard to check a packed file which they cannot decrypt but that is a bit too easy!

AV software should be more intelligent, if they encounter a packed file it should execute it inside its own sandbox and then check the results. It will be hard to make this foolproof but it is possible.

[Joe Forster/STA]

Some anti-malware software, actually, do this but those are rather called HIPS than anti-virus. E.g. the free Comodo Firewall has a built-in sandbox which, as far as I remember, has a semi-automatic community-driven online database of whichever file is or isn't malware and you can also submit (I guess, only the checksum of) your own "suspicious" files there. Such sandboxes to become common is, I think, still a bit into the future, especially for fully automated ones.