A backpack hijacker would give you a link with a message. This person will add you if you are rich and trade all of his items for all your items, if you click the link it will pop up a steam validator thingy. DONT CLICK IT AND DONT EVER RUN IT! Heres a message i was sent and fell for. "Hey dude i got a friend name's Alex. He cant add you for a reason so add him , be quick as wel though. This is the link to his account. blah blah blah. the steamcommunity part is mispelled like steamcomuniityy or something close. Dont fall for this bullshit like i did. Take care all those TF2 players and be safe. These fuckers need to be taught a lesson but sadly us normal players cannot do a single shit about it. Be safe