Abstract

A key way in which banks mitigate the effects of phishing attacks is to remove the fraudulent websites and abusive domain names hosting them. We have gathered and analyzed empirical data on phishing website removal times and the number of visitors that the websites attract. We find that website removal is part of the answer to phishing, but it is not fast enough to completely mitigate the problem. Phishing-website lifetimes follow a long-tailed lognormal distribution—while many sites are removed quickly, others remain much longer. We have found evidence that one group responsible for half of all phishing, the rock-phish gang, cooperates by pooling hosting resources and by targeting many banks simultaneously. The gang’s architectural innovations have significantly extended their websites’ average lifetime. Using response data obtained from the servers hosting phishing websites, we also provide a ballpark estimate of the total losses due to phishing.

Phishing-website removal is often subcontracted to specialist companies. We analyze three months of `feeds’ of phishing website URLs from multiple sources, including two such companies. We demonstrate that in each case huge numbers of websites may be known to others, but the company with the take-down contract remains unaware, or learns of sites only belatedly. Upon calculating the resultant increase in lifetimes caused by the take-down company’s lack of action, the results categorically demonstrate that significant amounts of money are being put at risk by the failure to share proprietary feeds of URLs.

Finally, we have studied how one anti-phishing organization has leveraged the so-called `wisdom of crowds’ by relying on volunteers to submit and verify suspected phishing sites. We show its voting-based decision mechanism to be slower and less comprehensive than unilateral verification performed by companies. We also find that the distribution of user participation is highly skewed, leaving the scheme vulnerable to manipulation.