recently i discovered doing otc that its possible to buy dirty bitcoins from someone and then when you try to sell it on an exchange the account gets frozen 
does anyone know how to know if a btc is clean this ?
kind regards
Yeah, that’s a real risk in OTC. If you buy BTC that’s been through shady stuff (e.g. hacks, darknet, etc.), some exchanges can flag it and freeze your account.does anyone know how to know if a btc is clean this ?
kind regards
Best way to stay safe? Use tools like AMLBot or Chainalysis-style checkers to scan wallet addresses before you buy. Not perfect, but way better than getting stuck with "dirty coins."