State-level public assistance agencies completed nearly a million SNAP fraud investigations in fiscal year 2016. These investigations hinge on compiling incriminating information about clients. Drawing on interviews with welfare fraud workers in five U.S. states, this article shows how fraud investigators creatively exploit clients’ social networks to extract such information, and thus use clients’ social ties against them. Investigators gain some information through elective cooperation, when people voluntarily implicate others. Fraud workers say these denunciations typically arise from negative-valence ties (bad blood). Other times, investigators co-opt neutral or positive-valence ties (good will) for enforcement purposes. This co-optation includes eliciting information from unwitting acquaintances and exploiting clients’ own online social networking activity. These findings demonstrate social ties’ appropriability, through which they serve as resources for relational outsiders’ interests. Repurposing welfare clients’ social ties for fraud enforcement presents a two-fold threat to subsistence and social mobility prospects: it imposes punishments—including program disqualifications—while simultaneously damaging social support networks. These enforcement practices reveal appropriability as an unrecognized property of social ties, particularly for socioeconomically marginalized people, and constitute a noteworthy element of contemporary poverty governance.