Re: Do we need attachments?
You can blame Microsoft but at least they changed the file format to differentiate between document sand macro carrying documents (so trivial to block) at least 10 years ago.
I hadn't even realised until recently that PDF files can contain and execute javascript and carry secondary, launchable documents within their payload. I had assumed any pdf nasties were just through the backdoor with specially crafted documents exploiting bugs, not through the front door using adobe reader's features.