By the way, in all the times I've spotted cheaters at the DoN SnGs I always won the game. So if you were playing the $5.40 DoNs in the last 2-3 months and got an email from stars about a refund due to being cheated feel free to leave a thank you in the comments. :) At least that way I get something out of it.
In this case I suspected there might be something fishy going on before the game even started. I joined this particular game to have a close look at the action. It turns out my hunch was right.
Here's a look at some of their plays that I reported to PokerStars. Maybe it'll help you spot cheaters at your table. (By the way, PokerStars chooses not to reveal the identity of the cheats to other players so I have changed the names of all players at the table.)
In this hand, cheater-2 is the short stack at the table with just over 2 big blinds left. Cheater-1 isn't in much better shape but he decides to help out cheater-2. This looked like an obvious case of chip dumping and stack balancing. Cheater-1 raises to try and get heads-up with cheater-2 and then folds when cheater-2 shoves 70 chips on the flop.
A few hands later and cheater-2 is in rough shape once again while cheater-1 has a very healthy stack. Cheater-1 raises from late position with a very bad hand and cheater-2 calls with a marginal hand.
While it's not uncommon for a player to attempt to steal the blinds in this spot with a hand such as Q5o, flat calling over 90% of your stack with 89o is a pretty bad move. Leaving yourself with only 70 chips behind isn't enough for a stop and go so if you choose to play a hand in this spot the right move is to shove all in pre flop. Either way, the original raiser has the right pot odds to call with anything on the flop. The same thing happened the previous hand but the cheater folded, obviously to dump chips.
The point of raising preflop is so that both cheaters can isolate each other and be heads up. They check it down to the river and when it's determined that cheater-2 has the best hand, cheater-1 is willing to call a small shove on the river with air. I folded in this spot because I didn't want to get involved in hands between these two players. At this point I was pretty certain what was going on.
This was the last suspicious hand of the game. Cheater-2 must be pretty weak as he's once again the short stack at the table and left with less than 1 big blind after posting. Player-3 is also pretty short but he raises from the cutoff position to get cheater-2 all in and end the game. To protect the short stack cheater, cheater-1 shoves all-in. Now cheater-2 folds and when it gets around to player-3 he has a tough decision. With a player left with 1BB at the table player-3 decides to fold and try and wait out cheater-2. You'll notice I make a pretty nitty fold here. That's because after being pretty certain that there were two cheaters at the table, I was fairly certain the hand would play out exactly as it did. There was no need for me to get involved since I was pretty much guaranteed a win.
The next hand, player-3 was UTG and picked up a decent hand and shoved. He had to as he was going to hit the blinds next hand. Two players called, including cheater-1. There was nothing odd about that hand other than the fact that this time, cheater-1 didn't shove over the top with a good hand. Player-3 lost that hand to another player that called along with cheater-1. Cheater-1 had the sense to check it down even after he hit his hand. Cheater-2 won the game with only 50 chips left after posting the small blind.
I've run across and helped bust 6 cheaters so far. It's something to try and keep an eye out for but it's a small percentage of the thousands of players I've been up against at these games. So it's nothing to go crazy over. PokerStars is very good at catching and dealing with online poker cheating but we also need to help out where we can if we see something that's just not right.
If you see stuff like this at your table, don't say anything in chat. Copy all the suspicious hands between the two suspected cheaters and email them to email@example.com with details on why you think this was cheating. They'll review both players' histories with all cards face up as well as other games they played together and make a determination. In this case, it looked like they suspended their accounts while the investigation was under way.
These 3 hands alone aren't enough. One thing that stood out was that these two players, especially cheater-1, were very aggressive against other players but were soft playing each other.
Another thing you might want to look at is if they seem to play a lot of games together. You can do this by going to PokerProLabs.com and doing a search for one of the players. Then scroll down and look at their Last 10 Poker Tournaments. If you click on each link in that list, it will show you all the players entered in that game.
The reason you don't want to say anything in chat is because you don't want to let them know you're on to them. They might change their play and throw off the investigation. You also might be wrong. Some people do stupid things. They're not cheating, they just don't know any better. One hand or one game is not proof of cheating. PokerStars' review team will look at all hands they played face up and be able to make a more accurate assessment. They are also able to look into other factors that you can't.