CNT 5605, Fall 2015
Pentest Assignment
No journal is due for this assignment.

Assignment: Pentesting

As of distribution of this assignment on November 30, 2015 (Monday), each student can seek to compromise the machines of the other graduate system administration groups in the Networking Lab.

Attacks may continue until 5:00pm, December 9th, 2015 (Wednesday of finals week.)

Your grade in this exercise will reflect your success in securing your machine against the widest possible variety of attacks (with the exceptions noted below) and your success in gaining access to other students' machines.

On any machine that you successfully compromise, you are to open a "backdoor" shell requiring no authentication on a port of your choice that is greater than 35000. The test of a successfully compromised machine will be the ability to use either nc IPNUMBER PORT or telnet IPNUMBER PORT to get access to a bash shell on the machine. Alternatively, you may start a "reverse backdoor" going to port 49999 on machine; this reverse backdoor must try to connect at least once every five minutes, and provide a shell prompt to any ordinary "nc" in listening mode (i.e., this should be in the clear, and not using SSL.)


PURPOSE OF EXERCISE. Knowledge of the techniques used by attackers must be understood to secure a network, which is one of the more critical jobs of the modern system administrator. Use what you learn in a responsible manner.

SCOPE OF USE. In this exercise, strictly limit all attacks and attempts to gain information to the other sysadmin machines in room 016; the only ip numbers you should test are 192.168.26.[100-229] Any use of such techniques or any such use on any other Computer Science machines or those of any other system is strictly prohibited.

NO ACTUAL DAMAGE. The goal of this exercise is to gain access; not to damage ANY portion of the target computer, including its filesystems or to cause ANY mischief whatsoever. DO NO DAMAGE. Just start up a backdoor shell or reverse shell.

NO PHYSICAL INTRUSION. For the purposes of this exercise, it will be assumed that each machine is physically secure. Therefore, no attempt may be made to gain physical access to the components of a given computer or to access said computer from the console. Attempting to boot said computer from an optical drive, flash drives, or other physical media attached to the subject computer is specifically prohibited. All access must be made over the network.

ACTS UPON INTRUSION. Upon starting a backdoor, immediately communicate the ipnumber and port to your instructor via email. You may NOT attempt the same attack until you have been notified that it's okay to do so, but once you have been notified, you may choose to make the same attack again to determine if the target team has made successful modifications.

USER ACCOUNTS / NORMAL SERVICES. Your Debian machine must continue to provide normal user services to local users (i.e., those people with a local account on the machine itself.) All services configured in earlier assignments must remain running and available, and in particular both ssh and your webservers must be available. This will be checked on a random basis. Don't turn OFF the machines for any reason. Your machines must also respond to ping, so don't firewall off ICMP ECHO packets.

PACKET SNIFFERS. Packet sniffing is allowed.

ARP POISONING: ARP poisoning is not allowed. It has historically been a successful technical technique for compromising machines, but ARP cache poisoning is highly disruptive.

DENIAL OF SERVICE. Denial of service attacks are not allowed (nor are likely to do anything useful in the current lab environment.)


  1. Can I turn off iptables on a pwned machine for my backdoor? Yes, you can turn off iptable blocking of up to four ports on a compromised host to allow incoming connections to your backdoor. However, this should not be a permanent change; use iptables -I to insert your temporary rules from the command line.
  2. Can I use port knocking to obscure my backdoor? Yes, you may, but the port knocking needs to be incorporated in your backdoor program. Do not install a separate daemon to do your portknocking, and don't reconfigure any existing knockd on the compromised machine.
  3. Can I use a kernel module rather than a userland process for the backdoor? Yes, you may, but you should insert the module by hand (for instance, with insmod), and it should not be automatically re-installed at reboot. This kernel module should be thoroughly tested before you install it on the target — and "thorough" means "tested on the same kernel as the target".
  4. Can I use a rootkit for the backdoor? Generally, no. However, as stated in 3, you can use a one-shot kernel module insertion. But you are not to change the target machine's kernel, shared libraries, or system binaries in any permanent fashion.
  5. Can I use my attack laptop in the lab? Yes, but you must use a wired connection. Consult with me if you want to do this.

If you compromise a machine, create a root reverse shell, and demonstrate it, you get 3 points on your final grade for the term (not just this assignment); if you can do it twice, you get 5 points added to your final grade.

I reserve the right to deny these additional points if I believe that you installed the backdoor by other means than a pure network compromise, such as by collusion or by physical compromise.

No journal for this assignment.