Đang chuẩn bị nút TẢI XUỐNG, xin hãy chờ
Tải xuống
This paper presents a detailed case study of the Clickbot.A botnet. The botnet consisted of over 100,000 machines and ex- hibited some novel characteristics while also taking advantage of some characteristics of existing, well-known botnets. One of the most novel characteristics of the clickbot is that it was built to conduct a low-noise click fraud attack against syndicated search engines. This paper focuses on describing the novel aspects of the Clickbot.A botnet, and describes parts of our experience in in- vestigating it. For instance, we describe how syndicated search engines work, and how Clickbot.A attacked such search en- gines. We believe that it is important to disclose the details of how such botnets. | Distributed Discrete-Event Simulation JAYADEV MISRA Department of Computer Sciences The University of Texas at Austin Austin Texas 78712 Traditional discrete-event simulations employ an inherently sequential algorithm. In practice simulations of large systems are limited by this sequentiality because only a modest number of events can be simulated. Distributed discrete-event simulation carried out on a network of processors with asynchronous message-communicating capabilities is proposed as an alternative it may provide better performance by partitioning the simulation among the component processors. The basic distributed simulation scheme which uses time encoding is described. Its major shortcoming is a possibility of deadlock. Several techniques for deadlock avoidance and deadlock detection are suggested. The focus of this work is on the theory of distributed discrete-event simulation. Categories and Subject Descriptors c.2.4 Computer-Communication Networks Distributed Systems distributed applications D.1.3 Programming Techniques Concurrent Programming D.4.1 Operating Systems Process Management deadlocks 1.6.1 Simulation and Modeling Simulation Theory General Terms Algorithms Theory Verification Additional Key Words and Phrases Asynchronous simulation deadlock detection and recovery deadlock prevention message communicating processes modeling interaction by message communication INTRODUCTION This survey presents an entirely new approach to the problem of system simulation. A system simulation is typically carried out as a repetition of the following sequential steps Fetch one event from a data structure carry out one step of simulation and possibly update the data structure. Such simulations are practical only when the number of events being simulated is modest. Recent advances in computer and communication systems have resulted in demands for new tools for their analyses. Mathematical modeling techniques have so far proved inadequate in dealing with these .
