Cross-Site Search Attacks

Cross-site search (XS-search) attacks circumvent the same-origin policy and extract sensitive information, by using the time it takes for the browser to receive responses to search queries. This side-channel is usually considered impractical, due to the limited attack duration and high variability of delays. This may be true for naive XS-search attacks; however, we show that the use of better tools facilitates effective XS-search attacks, exposing information efficiently and precisely. We present and evaluate three types of tools: (1) appropriate statistical tests, (2) amplification of the timing side-channel, by 'inflating' communication or computation, and (3) optimized, tailored divide-and-conquer algorithms, to identify terms from large 'dictionaries'. These techniques may be applicable in other scenarios. We implemented and evaluated the attacks against the popular Gmail and Bing services, in several environments and ethical experiments, taking careful, IRB-approved measures to avoid exposure of personal information.