For six years, a legal battle to unmask an anonymous informant has pitted an Arlington, Va.-based defense contractor, Solers Inc., against the Software & Information Industry Association, a Washington-based trade group trying to shield the John Doe’s identity.

The informant, through the trade group’s Web site, accused Solers in 2005 of using unlicensed computer software. Solers, an information technology services provider, conducted an internal investigation and notified the trade group that it used only properly licensed software. The company sued the informant for defamation in District of Columbia Superior Court in May of that year.