How do sites catch cheaters on cash games?

I read about this on serbian site.They didint write how poker sites find this guys,so i ask you??


Group sit on sam table,gruop have leader,They are in all time talk conncetion.
Victim is guy who sit vs this guys.This guys are probbabbly from sam country but not necessarily.This guys have payment from leader,and he take all cash what they won.
How poker sites fight with this group?

regs will notice suspicious behavior in playing patterns, the fact they always play together etc, and report it to the site. The site then reviews hand histories.

The sites also have software that will look for this kind of thing.