Unfortunately we've been receiving a high volume of private message SPAM accounts here on AP. We try to delete them as soon as they are identified and check the new registrations almost daily for accounts that look suspect. Those private messages are deleted when these bogus users are deleted. You might receive email notifications about new private messages when in fact there are no new messages in your box. This is nothing to worry about, it simply means we deleted this user before you checked your PM.
We are working on a fix to block spammers from sending PMs to people, but if you'd rather not receive the private message notifications at all in the meantime, of course you can change that setting by just editing your profile options.
And of course, just like with email security, do not open links or download files sent to you by people you don't know here on AP. Chances are, if you've never heard of them and they're posting a link that has nothing to do with Airsoft, it's a malicious link.
Thanks for bearing with us.