A common phenomenon in online discussion groups is the individual who baits and provokes other group members, often with the result of drawing them into fruitless argument and diverting attention from the stated purposes of the group. This study documents a case in which the members of an online community--a feminist web-based discussion forum--are targeted by a "troll" attempting to disrupt their discussion space. We analyze the strategies that make the troller successful and the targeted group largely ineffectual in responding to his attack, as a means to understand how such behavior might be minimized and managed in general. The analysis further suggests that feminist and other nonmainstream online forums are especially vulnerable, in that they must balance inclusive ideals against the need for protection and safety, a tension that can be exploited by disruptive elements to generate intragroup conflict.