"TANGODOWN - http://docomo-usa.com #lulzsec #antisec #StopCISPA We are lulzsec. The most wanted fleet. Bow to our feet," the hackers tweeted earlier today.
At this point, the site has been down for 18 hours.
As Cyber War News notes, NTT DoCoMo also published an announcement on its Web site over the weekend admitting that U.S. customers' personal information had been published on April 26, but noting that Japanese customers' information was not accessed.
The company says it will be contacting affected customers individually to offer assistance.