Review Questions

  1. What daemon is associated with the control files /etc/hosts.allow and /etc/hosts.deny?

  2. In general terms, describe a method to locate SUID programs in the local filesystem. Why might an administrator do this routinely?

  3. What is the danger of making /bin/vi SUID?

  4. Why should a user run ssh instead of telnet?

  5. Describe shadow passwords and the file where the passwords are stored. Why don’t we store encrypted password strings in /etc/passwd anymore?

  6. How can the tool /usr/sbin/lsof help you identify potential security issues?

  7. What is the difference between a hard limit and a soft limit, with regard to the ulimit command?

  8. Why is it advisable to use sudo rather than su in an environment with multiple administrators?

  9. What kinds of things can you ascertain about a remote system with the nmap command?

  10. Describe the process of key-based authentication between systems using ssh.

  11. What is the difference between a public and a private key? What are they used for?

  12. Describe how to encrypt a file with gpg.

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