Distributed denial of service (DDoS) attacks on The Final Fantasy XI virtual world have caused extended downtime within the past week, according to game publisher Square Enix. The attacks, which began April 9, raise the prospect that online games may be emerging as a new target for "DDoS blackmail" schemes.

"Recent technical difficulties with our PlayOnline server are due to a DDoS from anonymous third parties," Square Enix said in a message to users. "We have determined that this activity was undertaken with malicious intent and specifically targeted our network." The company said it has been working with law enforcement officials in the US, Japan and Europe, but has not yet isolated the source of the DDoS. "Attack methods have varied, which has caused a more time-consuming review of our network protection," Square Enix reported.

The company has not said whether it received any request for payment from the attackers. Industries conducting large volumes of transactions are targets for a cottage industry of digital extortionists using DDoS attacks. These attacks have previously targeted online betting sites and payment gateways.

Massively multiplayer online role-playing games (MMORPGs) can attract hundreds of thousands of subscribers, who each pay a monthly subscription fee for access to the game servers. While MMORPG credits are often measured in extra time rather than cash refunds, the games nonetheless experience a substantial cost of downtime. As of last fall, Final Fantasy XI reported more than 550,000 subscribers, who pay $12.95 a month for the game.