Phishing attacks to e-mail accounts. In Exercise 2.43 (p. 49), you learned that phishing d...

Phishing attacks to e-mail accounts. In Exercise 2.43 (p. 49), you learned that phishing describes an attempt to extract personal/financial information from unsuspecting people through fraudulent e-mail. Data from an actual phishing attack against an organization were presented in Chance(Summer 2007). The interarrival times, i.e., the time differences (in seconds), for 267 fraud box e-mail notifications were recorded and are saved in the PHISHING file. For this exercise, consider these interarrival times to represent the population of interest.

a. In Exercise 2.43 you constructed a histogram for the interarrival times. Describe the shape of the population of interarrival times.

---

b. Find the mean and standard deviation of the population of interarrival times.

---

c. Now consider a random sample of n= 40 interarrival times selected from the population. Describe the shape of the sampling distribution of , the sample mean. Theoretically, what are   and ?

---

d. Find P(<90).

---

e. Use a random number generator to select a random sample of n= 40 interarrival times from the population, and calculate the value of . (Every student in the class should do this.)

---

f. Refer to part e. Obtain the values of   computed by the students and combine them into a single data set. Form a histogram for these values of x. Is the shape approximately normal?

---

e. Use a random number generator to select a random sample of n= 40 interarrival times from the population, and calculate the value of . (Every student in the class should do this.)

---

g. Refer to part f. Find the mean and standard deviation of the -values. Do these values approximate   and , respectively?

---

f. Refer to part e. Obtain the values of   computed by the students and combine them into a single data set. Form a histogram for these values of x. Is the shape approximately normal? e. Use a random number generator to select a random sample of n= 40 interarrival times from the population, and calculate the value of . (Every student in the class should do this.)

Phishing attacks to e-mail accounts.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 e-mail. 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 e-mail account—called a “fraud box”—which enabled employees to notify it if they suspected an e-mail phishing attack. The interarrival times, i.e., the time differences (in seconds), for 267 fraud box e-mail notifications were recorded. Researchers 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. Construct a frequency histogram for the interarrival times. Give your opinion on whether the phishing attack against the organization was an “inside job.”