The U.S. Air Force has put its satellite jamming weapon, the Counter Communications System (CCS), into service early. Originally due for service sometime before 2010", the system went live this past September. 

The ground based CCS uses uses powerful radio signals to temporarily block communications to and from a satellite. CCS does not permanently damage satellites. This makes CCS a more diplomatic weapon, and one that does not further litter orbital space with more space junk. 

The air force would not release details of the system, or exactly how it works. They did say that it was built with off-the-shelf components for under $10 million. The system (or systems) is also mobile. More details on how CCS works probably wont be revealed until it is used for the first time. It is known that satellites can be jammed with existing radio jamming equipment if you can get your jammer close enough to where the material to be broadcast is uplinked (transmitted to the satellite.)