REUTERS/Steve Marcus
A report from ESET (via The Register) has unearthed the practice, which has affected hundreds of players on poker websites such as PokerStars and Full Tilt Poker.
The malware infects the player's computer, takes a screenshot of their hand, and then sends the unique ID of the player to the hacker. From here, the hacker can then find the player in the online poker rooms and play against them with knowledge of their hand.
ESET has been detecting the malware since March 2015 in various forms. Newer versions of the malware have an increased ability to access other parts of the computer, such as passwords.
While hacking online poker tournaments is rare, it is far from unprecedented and there is very little online poker companies can do to prevent it, as the malware is usually contracted from an outside source, such as a torrent download.