The SEC filed a civil lawsuit against Cuban in Dallas federal court. The SEC alleges that in June 2004, Cuban was invited to get in on a stock offering by Mamma.com after he agreed to keep the information private.
The SEC says Cuban knew the shares would be sold below the market price then. It says a few hours after getting the information, Cuban told his broker to sell his entire stake of 600,000 shares before the public announcement of the offering.
There's been no comment from Cuban.
Forbes magazine lists Cuban as one of the richest people in the world, said to have a net worth of $2.3 billion as of March 2007.