Unless you have done your research. I was listening to the latest CyberSpeak podcast yesterday (a very nice podcast by the way) and I heard the guy (Chad McMillan) who was being interviewed talking about a
revolutionary new technology for identifying packed executables by signature which he will be presenting at BlackHat. I wonder how many people who attend BlackHat know about PeID which does all the things this guy claims (including scanning for the packer in all the file not just at the entry point) and has a huge list of packers. And you can visit the forums for even more user contributed signatures.
Finally a note about the captcha image on the CyberSpeak podcast blog: I don't want to give any ideas to spammers, but from a technological stand point it is relatively week. I remembered the morphological filters from my image processing class and Gimp has already these implemented (unders Filters -> Generic). Below you can see an example captcha, the same image after the Dilate filter was applied and finally the same image with a Dilate and then an Erode filter applied. The main weaknesses in this captcha are that the noise is always one pixel in width (thus a single pass of Dilate eliminates it) and that the background is of solid color (thus it can easily be identified). The captchas generated by blogger are much better, but sometimes they can be funny.
And one final note: the dilated / eroded picture with the original picture applied over it as alpha mask (meaning that it's white only where both the original picture and the dialed / eroded picture is white):