A CentOS computer was exploited during a penetration test. During initial reconnaissance, the penetration tester discovered that port 25 was open on an internal
Sendmail server. To remain stealthy, the tester ran the following command from the attack machine:
Which of the following would be the BEST command to use for further progress into the targeted network?
The command set up an SSH tunnel from port 5555 on the attack machine to port 25 on an internal Sendmail server at IP address 10.10.1.2. To interact with the internal network through this tunnel, the proper approach is to use netcat to connect to the local port 5555, which is forwarded to the remote port 25 on the Sendmail server. Thus, using 'nc 127.0.0.1 5555' is the best choice to further this penetration test, as it allows the tester to communicate through the established SSH tunnel.
Port 25 from the remote host is forwarded to local port 5555 (to IP: 10.10.1.2). So if you have forwarded the port to yourself, it means you can access it by connecting to 127.0.0.1 or 10.10.1.2. Next part of the pentester task is to determine what service is opened on 25 or what communication is sent on internal service. Quickest way to do this is to use netcat. A - port 5555 is not specified B - port 5555 is not specified, why would you ssh to smtp port with sendmail server? C - correct, netcat may be utilized to “progress into the targeted network” and test SMTP. D - if there is no ssh connection on port 25 it is useless as above in B. Syntax is wrong, to specify port on ssh you need to use -p.
C. nc 127.0.0.1 5555 The command run by the penetration tester on the attack machine was used to establish a connection between port 5555 on the attack machine and port 25 on the internal Sendmail server at IP address 10.10.1.2. This creates a tunnel between the two machines, allowing the attack machine to access the internal network through port 5555. Therefore, to further progress into the targeted network, the best command to use would be "nc 127.0.0.1 5555" which would allow the tester to connect to the internal network through the tunnel set up on the attack machine.
The answer is C. nc 127.0.0.1 5555. By running this command, the penetration tester can initiate a connection to the Sendmail server on port 25 without having to route the traffic through their attack machine. This will keep their activities undetected and allow them to further progress into the targeted network.
To remain stealthy and make further progress into the targeted network after exploiting the CentOS computer, the penetration tester should use a command that takes advantage of the open port on the internal Sendmail server. The BEST command to use for further progress would be: A. nc 10.10.1.2 Explanation: • nc (Netcat): Netcat is a versatile networking tool that can be used for reading from and writing to network connections using TCP or UDP. By connecting to 10.10.1.2, the tester is likely attempting to interact with another internal service or machine in the network, leveraging the foothold they have gained. • Stealth and Port 25: Given that port 25 (SMTP) is open, the tester might use Netcat to connect to other services or relay messages through the Sendmail server.
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