Rockstar's open world shooter Grand Theft Auto IV clocked in at number one on the charts in Xbox Live online activity, Xbox Live director of programming Larry "Major Nelson" Hyrb's revealed on his blog.

For the week starting April 28, the title beat out Infinity Ward's Call of Duty 4: Modern Warfare and Bungie's Halo 3, which clocked in at second and third, respectively. Rankings are based on the number of unique users playing online while connected to Xbox Live.

GTA 4's top ranking knocks Call of Duty 4 off of a solid three-month streak at number one in online activity. The last game to supplant Call of Duty 4 was Halo 3 back in early January, shortly after the holiday blitz of new users hit Microsoft's online gaming service.

Microsoft has corrected the Xbox Live Gamertags of confirmed cheaters, citing violations of the company's terms of use, Xbox Live director of programming Larry "Major Nelson" Hyrb wrote on his blog today.

Accounts which Hyrb described as "the most serious offenders" were today stripped of their Gamerscore, resetting the total to zero. Moreover, those accounts will not be able to regain any previously obtained achievements—this does not, however, forbid the earning of future achievements in other games.

Violators have also been marked as cheaters on the Xbox.com community page, as evidenced in a sample provided by Hyrb. Infamous achievement hoarder StripClubDj, who was once lauded for being the first Xbox Live gamer to breach the 100,000 Gamerscore milestone, was among the marked accounts.

"Xbox Live remains committed to keeping the service free of cheating in order to maintain a fair and level playing field for everyone," Hyrb wrote.