When a person I don't recognize is listed as having been on my profile page, I first check the possible avenues through which they may have arrived there, i.e. checking if they've posted in the same threads as me.
If they do not fulfill that criterion, then... let's just say that when random people you've never seen before start popping up on your profile page, it usually means trouble.
The best way to counter a spai is to let them know that you know what they're up to.
But you already know that.