What's different with the new PDF only spams?

[Steve Campbell]

Seems like I just stopped seeing those PDF-Only spams using the SA rule 
that was posted here a week or so back.

Now, the rule seem to be insufficient and is letting a lot of the newer 
ones through. I'm not a RegEx expert, to be sure, so can any one offer a 
suggestion for a rule to stop this new wave PDF-Only mailings, please?

Thanks

Steve Campbell