Characterizing Internet worm spatial-temporal infection structures

Since the Morris worm was released in 1988, Internet worms continue to be one of top security threats. For example, the Conficker worm infected 9 to 15 million machines in early 2009 and shut down the service of some critical government and medical networks. Moreover, it constructed a massive peer-to-peer (P2P) botnet. Botnets are zombie networks controlled by attackers setting out coordinated attacks. In recent years, botnets have become the number one threat to the Internet. The objective of this research is to characterize spatial-temporal infection structures of Internet worms, and apply the observations to study P2P-based botnets formed by worm infection. First, we infer temporal characteristics of the Internet worm infection structure, i.e., the host infection time and the worm infection sequence, and thus pinpoint patient zero or initially infected hosts. Specifically, we apply statistical estimation techniques on Darknet observations. We show analytically and empirically that our proposed estimators can significantly improve the inference accuracy. Second, we reveal two key spatial characteristics of the Internet worm infection structure, i.e., the number of children and the generation of the underlying tree topology formed by worm infection. Specifically, we apply probabilistic modeling methods and a sequential growth model. We show analytically and empirically that the number of children has asymptotically a geometric distribution with parameter 0.5, and the generation follows closely a Poisson distribution. Finally, we evaluate bot detection strategies and effects of user defenses in P2P-based botnets formed by worm infection. Specifically, we apply the observations of the number of children and demonstrate analytically and empirically that targeted detection that focuses on the nodes with the largest number of children is an efficient way to expose bots. However, we also point out that future botnets may self-stop scanning to weaken targeted detection, without greatly slowing down the speed of worm infection. We then extend the worm spatial infection structure and show empirically that user defenses, e.g. , patching or cleaning, can significantly mitigate the robustness and the effectiveness of P2P-based botnets. To counterattack, we evaluate a simple measure by future botnets that enhances topology robustness through worm re-infection.

Waking the sleeping giant: Beliefs of Brazilian and *American teachers concerning liberation curriculum

The school curriculum is a matter mandated by the educational system rather than determined by the school stakeholders of a community, as Freire (1993) suggests. At the present time, one significant vision of school is challenging the current order of curriculum practice. It focuses on school as a liberating agency grounded on the belief that the abilities to access information and to think critically about it will educate an individual capable of making independent decisions. This dissertation investigates teacher's beliefs concerning curriculum. It was assumed that there is a discrepancy between what has been the position proposed by critical theorists including Freire (1998a, 1993); Apple (1979); Giroux (1998), and the position on curriculum which school systems are typically advancing. ^ There were four purposes of this study. The major purpose of this study was to determine whether or not Brazilian and American Teachers believe that a school curriculum based on Freirean principles could be implemented in the schools in which they worked. Also, this study sought to determine the differences found between teachers' beliefs in the Brazilian and American contexts. Another purpose was to determine how Brazilian and American teachers justify their beliefs and actions when these may represent conflicting values. Finally, this study sought to determine if these teachers believe that the curriculum is in need of change or if they accept the current curriculum as adequate. This study consisted of quantitative and qualitative data collection through multiple methods involving surveys and interviews. The study involved 171 teachers (88 Brazilian and 83 American) from multiple settings with the majority working for public systems. Overall, it seems that Brazilian and American teachers believe that a curriculum based on Freirean principles of education can be implemented in their schools, if ongoing education is provided. The majority of Brazilian teachers believe a curriculum change is necessary while half of the American teachers believe a curriculum change is needed and the other half seems to believe curriculum is adequate. Teachers explain that it is hard to implement a curriculum they believe to be most appropriate for students because the current curriculum is mandated by the school system or by national guidelines. The majority of Brazilian teachers and those American teachers who believed a curriculum change is necessary explained their rationale for change in terms of social justice, problem-solving, collective work, student-centered and context-based curriculum. American teachers, who believed that the curriculum is adequate, explained that they are satisfied with their student's achievements. They stated that their students are doing well on tests and are learning what is required. ^