Well there's new trade hack in USKO for example. You want to buy iron neck +0 and the hacker is selling one for you.
He puts Iron neck +0 in trade, but it can be old elemental neck or any iron neck looking necklace.
You will see old elemental neck in trade window as a "Iron neck +0", with all the same stats as iron neck +0.
After you have made trade, you will get old elemental neck even you saw iron neck +0 in trade window.
So there's somekind of new programs which changes the names/stats of items/uniques for a trade window, so I recommend you to fraps all bigger trades from now.
So you will have solid proof atleast if you get scammed, there's not really way to avoid this hack than trade with known people only.
Those scammers have an actual program to make this shit and they don't do 2x trades in this thingy, they just trade you once and puts iron neck +0 there and when you are done, you will get elemental neck or any other iron neck looking neck.
Someone will surely say something about the "Switching item scam in trades", but it's not that.
Like you trade first iron neck +0, then you cancel trade and trade again old ele neck and boom.
I haven't got scammed by this yet, but I've witnessed this already 2 times, so I'm here just to say watchout.
-There's program which changes item names/stats to the other items for a trade window for example. old ele neck to iron neck +0.
-Fraps all the big trades you make.
-Don't trade with nonames/1lvl naked people.