It is important to note that cheating has happened in the past in online poker games and might happen in future. These days all the big online poker sites have programs that automatically notice when cheating might be going on. Also the big online poker sites have employees whose only job is to prevent, find and stop cheating.
Most of the cheating in online poker happens in a form of collusion. Collusion is when two or more players share information about their hands with each other in order to try to win money from the player who doesn’t belong to their collusion ring.
For an example player A might reveal to player B over a phone that he is holding pocket aces and thus the player B should stay away from that pot. The easiest way to spot is collusion is to stay aware of weird betting patterns between players.
If you notice the same players always sitting in the same table, and especially if they are from the same location you should be especially cautious. If you suspect there is collusion going on in a game you should immediately contact the poker site’s support.