Cheating at Online Poker 
Cheating at online Poker does happen, despite vigilant efforts by Poker sites to prevent it. Here are some approaches that people use to cheat at Poker. We don't recommend that you try any of these, and you should know that most cheaters are easily caught. Things people have tried to cheat at Poker:

Abusing disconnect protect (DP)
Colluding with other players
Hacking the Poker software
Using a card scanner

Abusing disconnect protect (DP)

The "Disconnect Protect" feature is designed to protect your investment in a hand should your internet connection hiccup at a critical moment. Essentially, it lets you go to the showdown without having to call any remaining bets/raises to get there - your bets go into a side pot. This particular instance of online Poker can be abused by "pulling the plug" on your ethernet card at a critical moment in hopes of slopping your way to a win. Be warned, this is not only a lousy way to treat your opponents, but easily noticed by them and (more importantly) by the Poker software. Still, people use this tactic and the only way to avoid them is to join a table with "(no DP)" in its name, indicating that disconnect-protect is disabled.

Colluding with other player.

This is probably the most widely used technique for cheating at Poker- also known as "playing with your buddies". The concept is simple - fill most of the seats at your Poker table with people who all agree to share their pocket cards (by phone, IM, yelling, etc). Knowing what most of the other hands are is a tremendous [unfair] advantage to any player, and teaming up on unsuspecting non-buddies really puts the hurt on them. Most colluders get caught - Poker players are encouraged to report suspected collusion to the Poker sites, and they have all the digital footprints they need for proof. Most Poker sites believe in prevention - no two players with the same IP address can join the same table.

Hacking the poker software

Because online Poker networks depend on communication with the software running on each player's communication, it's tempting to think about intercepting or hacking that information. In particular, you probably want to know if there's some hack that will magically tell you what cards your opponents hold during the hand. While it is true that any piece of software has the potential to be compromised, Most Poker sites have erected legal and technical barriers to hacking their software. The player software is very adept at detecting and/or blocking potential intrusions into its data stream or programming.

Using a card scanner

Here's the ultimate pipe dream - some kind of software or robot that scans each hand you're dealt, does the math, and makes most (or all) of your plays for you. You'd start it first thing in the morning, and by the end of your second nap that day, it would have accrued a bunch of money in your account. I've written an entire article about the idea of a Poker scanner. A key point was this: a computer that plays every hand precisely by the odds might make a little bit of money, but not a windfall. The most profitable hands in Poker are often ones you had no business playing in the first place - low pocket pairs that make trips, a flush draw that hits on the river, etc. There's no getting around the fact that good Poker is a human game.