It should come as no surprise really.  True, Microsoft may be the king of the office, but eventually something was going to replace those poisoned Word docs, Excel spreadsheets, and PowerPoint presentations.  And if something was going to do it, it was going to be something easily as cross-platform and heavily used.

That something, was Adobe Reader PDF files.

At least, so says F-Secure.

And the reasoning, besides the obvious of being a cross-platform big target?  Well all of the vulnerabilities, of course!  I mean who in the security world doesn’t know that Adobe = holes.  It’s enough to rival Microsoft.  Apparently.  Which is why 2009 saw 49% of attacks targeting Adobe Reader through its vulns.

Clearly it should go without saying, if you don’t know why someone would send you a file, don’t open it.  And if you’re not sure, ask.  All of the poisoned documents in the world do no harm if you’re smart enough to not open them in the first place.