One of the toughest tasks facing Viktor Yushchenko as Ukraine's new president likely will be overhauling the State Security Service, the KGB successor agency alleged to have been involved in an array of devious and deadly activities. The cases of other Soviet-bloc countries show that success or failure could determine how well democracy takes root in Ukraine _ but the issue is complicated by indications that security forces played a role in averting a crackdown on Yushchenko's "Orange Revolution." Since the 38,000-strong State Security Service, or SBU, was formed in 1991 after independence from the Soviet Union, it is alleged to have been connected to organized crime, shady weapons deals and the deaths of several prominent opposition politicians and journalists. It is suspected of involvement in the September dioxin poisoning of Yushchenko, which took him off the campaign trail for weeks and left his face badly disfigured. He fell ill within hours of having dinner with top SBU officials.