Public disclosure websites (PDW)—sites like WikiLeaks—constitute a serious security challenge to the United States and other nations. PDW activists are dedicated to exposing sensitive government and commercial information in the belief that they are acting in the public good. As a result, PDWs have revealed hard-to-find, strategic and tactical level information that benefits the resiliency and operations of insurgent, terrorist, and criminal groups. To date, there is no evidence linking PDWs to an attack by violent nonstate groups, but this threat is almost certain to grow as Internet access expands globally. Given the high likelihood of future leaks, the U.S. Government should adopt stronger controls to safeguard information, including new legislation to address leaking, as well as tailoring “need to share” practices. Left unchallenged, PDWs imperil the ability of the United States to counter violent nonstate groups.