The recording industry has stepped up its campaign against campus music swapping, filing suit against four university students who operated file-search services on their school's internal networks.

The lawsuits, filed against two students at Rensselaer Polytechnic Institute (RPI), and one each at Princeton University and Michigan Technological University, ratchet up the pressure that the Recording Industry Association of America (RIAA) recently has been putting on universities to block campus file-trading. The trade group still has not filed suit against average file-swappers who use more common services such as Kazaa, however.

Read more: CNet News.