Warning: Possible virus-spreaders through steam!

[Wood]

Indeed, I actually know what software people use for this as I saw it on the Leak Forums the other day. It can be used via php, or just a java script that'll DL on people clicking the link and it'll send all the TF2 items, or CS:GO items to a certain person (most likely the guys account you met) which is almost 100% just a holding account and that'd be why you couldn't trade with him. He'll then pass the items onto another account, or just sell them on websites like hack forums and Leak Forums.