Can an email attachment be configured to, in some way, notify the sender upon opening and other details?

I do not necessarily mean in a malicious way, but can normal-looking attachments like PDFs have some kind of hidden function to let the sender know information about the recipient, specifically, attachments received in Gmail?

  • That's going to depend on the nature of the attachment. It really has nothing to do with Gmail; Gmail is simply the delivery mechanism. If you are concerned about the security of the PDF format, perhaps Information Security would be a better place for your question. – ale Apr 23 '15 at 12:48
  • It is not the attachment instead it should the file which is affected by unknown programs. – Vembu Apr 23 '15 at 15:26
  • Ok thanks I just asked because I thought Gmail was great at auto-scanning unwanted programs? – Seeder Apr 25 '15 at 18:22

In short, yes, this is entirely possible.

Many types of files can have metadata set to notify the sender when the attachment is opened. Since this usually isn't seen as malicious, Gmail's attachment scanning is not likely to flag it.

  • Is there a way to know which emails contain that kind of stuff? – Seeder Apr 23 '15 at 7:49
  • For attachment file, you will be able to find them with a good antivirus. – John Hill Apr 23 '15 at 12:08
  • For attachment file, you will be able to find them with a good antivirus. For link to images, just look if there are external link in the email and if there is an id instead of a direct link. Ex: mysite.com/img/image1.jpg is ok and mysite.com/img/image1.jpg?id=123456 will certainly inform the server that you have open the email. If it is present in the attachment (HTML page as example), it will do the job as well. Most email for advertisement contain this kind of stuff to know if you have open the email or not. – John Hill Apr 23 '15 at 12:15

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