The alleged subterfuge on UltimateBet.com — one of the 10 top poker sites — is the biggest known case of fraud targeting an Internet gambling site and its customers, according to the company that owns the site. It is similar to a case of cheating that occurred last year on UltimateBet’s sister site, AbsolutePoker.com, but this time the thieves ran the scheme for far longer — at least from January 2005 to January 2008, it said.

Word of the $75 million U.S. claim ($80 million Canadian) — the first indication of the scope of the alleged cheating — emerged this week when msnbc.com contacted a court-appointed liquidator overseeing the voluntary dismemberment of Excapsa Software Inc. of Toronto, which formerly owned and licensed the poker software to UltimateBet and other gambling sites. The claim was filed by Blast-Off Ltd. of Malta, a private company that currently has an ownership interest in Ultimate Bet.