LPI Linux Certification in a Nutshell, 2nd Edition

System Security (Topic 2.212)

Review Questions

1. Which file is considered first by TCP wrappers, hosts.allow or hosts.deny?

2. Why is it a good idea to store the Tripwire database on a read-only medium, such as a CD-ROM disk?

3. You have configured an internal network to use the 192.168.2.0/24 block of IP addresses. You have also configured a Linux system with two NICs and have enabled IP address forwarding. However, no users can access the Internet. You have decided not to use a proxy server. What else can you do to allow Internet access through your Linux router?

4. Consider the following line in the /etc/ssh/ssh_config file. What does it instruct sshd to do?

   Protocol 2

5. You have been asked to use the iptables command to configure a system to automatically drop all connections from systems that attempt to access TCP ports 21 through 80 on your local system. Your supervisor wants this rule to be the first rule processed. Write in the command that will accomplish this.

6. Why do many FTP servers contain their own copies of files such as ls, passwd, and chmod?

7. You wish to use public-key authentication for an SSH session with a remote user. What must you first place into your ~/.ssh/authorized_keys or ~/.ssh/ authorized_keys2 file?

Answers

1. The hosts.allow file is considered first. Then TCP wrappers reads the contents of the hosts.deny file.

2. Because storing the database on a read-only medium helps make you reasonably sure that the database has not been changed.

3. Use iptables to enable Network Address Translation ...