Refer to the Chance  (Summer, 2007) article on phishing attacks at a company,  Exercise 2.24. Recall that phishing describes an attempt  to extract personal/financial information through fraudulent email. The company set up a publicized email  account—called a “fraud box”—which enabled employees  to notify them if they suspected an email phishing attack. If there is minimal or no collaboration or collusion  from within the company, the interarrival times (i.e., the  time between successive email notifications, in seconds)  have an approximate exponential distribution with a mean  of 95 seconds.  a. What is the probability of observing an interarrival  time of at least 2 minutes?  b. Data for a sample of 267 interarrival times are saved in  the PHISHING file. Do the data appear to follow an  exponential distribution with β = 95?

Data from Exercise 2.24

Phishing is the term used to describe an attempt to extract personal/financial information (e.g., PIN numbers, credit card information, bank account numbers) from unsuspecting people through fraudulent email. An article in Chance (Summer, 2007), demonstrates how statistics can help identify phishing attempts and make e-commerce safer. Data from an actual phishing attack against an organization were used to determine whether the attack may have been an “inside job” that originated within the company. The company set up a publicized email account — called a “fraud box” — which enabled employees to notify them if they suspected an email phishing attack. The interarrival times, i.e., the time differences (in seconds), for 267 fraud box email notifications were recorded. Chance showed that if there is minimal or no collaboration or collusion from within the company, the interarrival times would have a frequency distribution similar to the one shown in the accompanying figure. The 267 interarrival times are saved in the PHISHING file.

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0.012 0.010 0.008 0.006 0.004 0.002 0.000 100 200 300 400 500 600 Time Differences Relative Frequency