Activision Blizzard - makers of game hits such as Call of Duty and World of Warcraft - have taken “aggressive” legal moves against gamers who use illegal software to cheat in games - in particular, the hit strategy title Starcraft 2.

“Cheat” software, such as the Starcraft 2 cheats that are commonly available, circulates freely or is sold illegally, and often carries a payload of malware. Some reports have claimed that up to 90% of such “add-on” software carries malware.

Silicon Republic reports that the move - a highly unusual one - targets one of the many Starcraft 2 cheats, ValiantChaos MapHack, which allows gamers to issue commands to characters faster in the strategy game. It clearly works - gamers pay a $62 "donation" to use it.

“The hacks and cheats made available by Defendants, including a product known as the ‘ValiantChaos MapHack’, modify the StarCraft 2 online game experience, to the detriment of legitimate StarCraft 2 users, and thus to Blizzard itself,” reported Torrentfreak.

The site noted that while the wording of the complaint focused on the “experience”, the actual charges related to copyright infringement. The group who make the popular “hack” is not known.

“Defendants create and sell their unlawful software products with the knowledge that they are facilitating and promoting users to infringe Blizzard’s copyrights, to breach their contracts with Blizzard, and to otherwise violate Blizzard’s rights,” the company said. The suit also alleges that, the hack “cause serious and irreparable harm to Blizzard and its products.”

The case is highly unusual: use of hacks in gaming is often punished by a temporary or permanent ban from the game for that user account, or other in-game penalties such as loss of game currency. Starcraft is a major player in competitive gaming, and fills football stadiums in Korea.

Speaking to the BBC, analysts described the move as “aggressive”.

"The only reason that cheats like this exist is because there is demand for them," said Ed Barton, an analyst at game consultancy Ovum. "But the competitive scene for Starcraft is very important, especially in Korea, and Blizzard needs to preserve the fantasy of the core experience."

The suit alleges, "The competitive aspect of Starcraft 2's multiplayer environment is one of the driving forces behind sales of the game. In fact, the Starcraft game are played as a competitive sport around the world, with professional or semi-professional players competing for national and international titles.”

In recent months, following the raft of available Starcraft 2 cheats, competitive gamers have switched allegiance to rival products such as League of Legends. Game site VG247 reported that the organization Major League Gaming had switched to the similar strategy game League of Legends, in addition to reducing prize money from $75,000 to $25,000.