Question

(For questions 1-4)

P(windows) = 0.5 P(macOS) = 0.2 P(Linux) = 0.2 P(other) = 0.1

1. If there are 800 total systems, how many of them are running the Linux operating system?

2. What is the probability that a system is NOT running MacOS?

3. A small organization has 200 systems but is only able to patch Microsoft operating systems automatically. How many unpatched Linux systems does the organization need to manually update?

(For questions 4-5) P(vulnerability 1) = 0.4 P(vulnerability 2)= 0.3 P(vulnerability 3) = 0.3

4. What is the probability that a given system is susceptible to Vulnerability1 and Vulnerability3?

5. A small organization has 200 systems. How many systems are probably affected by all three vulnerabilities?

Answer 1

1)

number of them are running the Linux operating system =np =800*0.2 =160

2)

probability that a system is NOT running MacOS =1-P(MacOS) =1-0.2 =0.8

3)Number of unpatched Linux systems does the organization need to manually update

=200*0.2 =40

4)Assuming independence

probability that a given system is susceptible to Vulnerability1 and Vulnerability3

=0.4*0.3=0.12

5)P( affected by all three vulnerabilities ) =0.4*0.3*0.3=0.036

therefore expected number affected by all three vulnerabilities =np=200*0.036 =7.2