Four of the five main online forums that al-Qaeda's media wing uses to distribute statements by Osama bin Laden and other extremists have been disabled since mid-September, monitors of the Web sites say. At the same time, in an apparently unrelated flare-up of online sectarian hostility, Shiite and Sunni hackers have targeted Web sites associated with the other sect, including that of a Saudi-owned television network and of Iraq's most revered Shiite cleric.