[Mimedefang] Image spam and broken file formats

[Kenneth Porter]

Do the files found in image spam follow the letter of the format specs, or 
do they tend to be broken? Is the degree of brokenness useful as a spam 
metric?

I'm a fan of rejecting broken files at the gateway (including HTML) and 
would like to bounce images that violate their format standards, as they're 
likely to cause issues like buffer overruns in unsuspecting clients.

Are there any good utilities that simply validate file formats commonly 
seen in email? I'd like to at least hit JPEG, GIF, PNG, and Acrobat.