I recently received a PDF file that, when attached to a gmail message, causes a warning to be displayed as follows:
Encrypted attachment warning – Be careful with this attachment. This message contains 1 encrypted attachment that can't be scanned for malicious content. Avoid downloading it unless you know the sender and are confident that this email is legitimate.
However, I am able to open the file without getting prompted for a password. I followed the advice given in this security stack exchange question and used the
pdfid.py program whereupon I got the below output:
/Encrypt flag that's set on the above output.
Why is Gmail telling me that the file is encrypted even though I can open it without being prompted for a password and would that, on its own, be reason for concern?