Masquerade attacks are a common security problem that is a consequence of identity theft. Masquerade detection may serve as a means of building more secure and dependable systems that authenticate legitimate users by their behavior. Prior work has focused on user command modeling to identify abnormal behavior indicative of impersonation. This paper extends prior work by modeling user search beh...

This paper describes analyses of the repeated use of search engines. It is shown that users commonly re-issue queries, either to examine search results deeply or simply to query again, often days or weeks later. Hourly and weekly periodicities in behavior are observed for both queries and clicks. Navigational queries were found to be repeated differently from others.

Annually, web search engine providers spend more and more money on documents ranking in search engines result pages (SERP). Click models provide advantageous information for ranking documents in SERPs through modeling interactions among users and search engines. Here, three modules are employed to create a hybrid click model; the first module is a PGM-based click model, the second module in a d...

Random walk methods and diffusion theory pervaded ecological sciences as methods to analyze and describe animal movement. Consequently, statistical physics was mostly seen as a toolbox rather than as a conceptual framework that could contribute to theory on evolutionary biology and ecology. However, the existence of mechanistic relationships and feedbacks between behavioral processes and statis...

Phylogenetic analysis is used in all branches of biology with applications ranging from studies on the origin of human populations to investigations of the transmission patterns of HIV. Most phylogenetic analyses rely on effective heuristics for obtaining accurate trees. However, relatively little work has been done to analyze quantitatively the behavior of phylogenetic heuristics in tree space...

We examine prior and current sponsored search auctions and find evidence of strategic bidder behavior. Between June 15, 2002, and June 14, 2003, we estimate that Overture’s revenue from sponsored search could have been more than 60% higher if it had been able to prevent this strategic behavior. We also show that advertisers’ strategic behavior has not disappeared over time; rather, such behavio...

The oceans are nutritionally dilute, and finding food is a major challenge for many zooplanktonic predators. Chemodetection is necessary for successful preycapture, but little is known about the infochemicals involved in the interaction between herbivorous copepods and their phytoplankton prey. We used females of Temora longicornis to investigate chemodetection of dimethyl sulfide (DMS) in this...

one of the most important extensions of the capacitated vehicle routing problem (cvrp) is the vehicle routing problem with simultaneous pickup and delivery (vrpspd) where customers require simultaneous delivery and pick-up service. in this paper, we propose an effective ant colony optimization (eaco) which includes insert, swap and 2-opt moves for solving vrpspd that is different with common an...

In this paper we undertake a large-scale study of online user search behavior based on search and toolbar logs. We identify three types of search: web, multimedia, and item. Together, we show that these different flavors represent almost 10% of all online pageviews, and indirectly result in over 21% of all pageviews. We study search queries themselves, and show that more than half of them conta...

Modeling User Behavior and Attention in Search