More big-time spammers may find themselves doing longer stretches behind bars if a federal judge's first-of-its-kind sentencing decision in a Denver case becomes widely applied.

At issue in this case, which featured testimony from Microsoft anti-spam experts, was the thorny matter of determining the actual financial harm to ISPs done by a particular spammer over a particular period of time. When Congress enacted the CAN-SPAM Act of 2003 it anticipated this difficulty and included language allowing for a spammer's profits to be considered in sentencing when financial damages caused by his crimes could not reasonably be calculated.

Last month, U.S. District Judge Lewis Babcock accepted a Colorado prosecutor's contention that this case, the United States vs. Min Kim, represented just such a situation. Microsoft says this is the first time a judge has applied CAN-SPAM sentencing guidelines in this manner.