  Whistleblower laws protect individuals who inform the public or an authority
about governmental or corporate misconduct. Despite these laws, whistleblowers
frequently risk reprisals and sites such as WikiLeaks emerged to provide a
level of anonymity to these individuals. However, as countries increase their
level of network surveillance and Internet protocol data retention, the mere
act of using anonymizing software such as Tor, or accessing a whistleblowing
website through an SSL channel might be incriminating enough to lead to
investigations and repercussions. As an alternative submission system we
propose an online advertising network called AdLeaks. AdLeaks leverages the
ubiquity of unsolicited online advertising to provide complete sender
unobservability when submitting disclosures. AdLeaks ads compute a random
function in a browser and submit the outcome to the AdLeaks infrastructure.
Such a whistleblower's browser replaces the output with encrypted information
so that the transmission is indistinguishable from that of a regular browser.
Its back-end design assures that AdLeaks must process only a fraction of the
resulting traffic in order to receive disclosures with high probability. We
describe the design of AdLeaks and evaluate its performance through analysis
and experimentation.
