An article in Information Security Technical Report [Malicious SoftwarePast, Present and

Chapter 3, Problem 3-89

(choose chapter or problem)

An article in Information Security Technical Report [Malicious SoftwarePast, Present and Future (2004, Vol. 9, pp. 618)] provided the following data on the top ten malicious software instances for 2002. The clear leader in the number of registered incidences for the year 2002 was the Internet worm Klez, and it is still one of the most widespread threats. This virus was first detected on 26 October 2001, and it has held the top spot among malicious software for the longest period in the history of virology. Place Name % Instances 1 I-Worm.Klez 61.22% 2 I-Worm.Lentin 20.52% 3 I-Worm.Tanatos 2.09% 4 I-Worm.BadtransII 1.31% 5 Macro.Word97.Thus 1.19% 6 I-Worm.Hybris 0.60% 7 I-Worm.Bridex 0.32% 8 I-Worm.Magistr 0.30% 9 Win95.CIH 0.27% 10 I-Worm.Sircam 0.24% The 10 most widespread malicious programs for 2002 (SourceKaspersky Labs). Suppose that 20 malicious software instances are reported. Assume that the malicious sources can be assumed to be independent. (a) What is the probability that at least one instance is Klez? (b) What is the probability that three or more instances are Klez? (c) What are the mean and standard deviation of the number of Klez instances among the 20 reported?