This screencast demonstration of the backscatter filtering and engine definition update options in the Forefront Protection for Exchange console covers some sample powershell commands you can use to configure SPAM filtering.
Watch it out at http://technet.microsoft.com/en-US/edge/Gg601132(MSDN.10)?query=1
Cheers,
Anderson Patricio
http://blogs.msexchange.org/patricio
Twitter: @apatricio