Poster: Thinking Inside the BLAC Box Smarter Protocols for Faster Anonymous Blacklisting

The Internet can be a dangerous place to visit. As the proportion of our daily activities that oc-cur online continues to increase, so too does our exposure to online privacy risks imposed on us by fraudsters and identity thieves, by intrusive adver-tising companies, by oppressive governments, and by countless unknown others. Anonymous commu-nications systems like Tor1 mitigate some of these threats by helping users to access services over the public Internet while concealing their identities and usage patterns from prying eyes. A global user base leverages the anonymity afforded by Tor and other anonymous communication systems to circumvent online censorship, to research taboo and unpopular subjects, and to speak their minds without fear of retaliation. Not only is this a win for privacy and free speech on the Internet, but it is also a potential boon for many online communities that might benefit from added diversity in their respective user populations. Compelling examples of such online communities include collaborative encyclopedias like Wikipedia2 and community-driven review sites like Yelp3. Yet reality is rarely so simple. The providers of such online services must ultimately weigh the expected benefits (both to themselves and to their user com-munities) of more inclusivity against the risks posed by abusive users, especially those who would hide behind the veil of anonymity to skirt accountability for their actions. A number of popular services— notably including Wikipedia, Yelp, Slashdot4, Craigs-list5, and most major IRC networks [10]—presently block contributions from anonymous users, despite the implied loss of diversity and the broader implications for free speech and the open exchange of knowledge and ideas