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Meterpreter

The Meterpreter Payload is a specific type of multi-faceted, extensible Payload that uses DLL injection to ensure the connection to the victim host is stable and difficult to detect using simple checks and can be configured to be persistent across reboots or system changes. Furthermore, Meterpreter resides entirely in the memory of the remote host and leaves no traces on the hard drive, making it difficult to detect with conventional forensic techniques. It is dubbed the swiss army knife of pentesting, and for a good reason. The purpose of Meterpreter is to specifically improve our post-exploitation procedures, offering us a hand-picked set of relevant tools for more straightforward enumeration of the target host from the inside. It can help us find various privilege escalation techniques, AV evasion techniques, further vulnerability research, provide persistent access, pivot, etc.

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Running Meterpreter

To run Meterpreter, we only need to select any version of it from the show payloads output, taking into consideration the type of connection and OS we are attacking. Whenever the Meterpreter Payload is sent and run on the target system, we receive a Meterpreter shell. We can then immediately issue the help command to see what the Meterpreter shell is capable of.

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Using Meterpreter

We have already delved into the basics of Meterpreter in the Payloads section. Now, we will look at the real strengths of the Meterpreter shell and how it can bolster the assessment’s effectiveness and save time during an engagement. We start by running a basic scan against a known target. We will do this a-la-carte, doing everything from inside msfconsole to benefit from the data tracking on our target.

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MSF - Scanning Target

However, looking at both the end of the webpage and the result of the Nmap scan more closely, we notice that the server is running Microsoft IIS httpd 6.0. So we further our research in that direction, searching for common vulnerabilities for this version of IIS. After some searching, we find the following marker for a widespread vulnerability: CVE-2017-7269. It also has a Metasploit module developed for it.

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MSF - Searching for Exploit

We proceed to set the needed parameters. For now, these would be LHOST and RHOST as everything else on the target seems to be running the default configuration.

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MSF - Configuring Exploit & Payload

We have our Meterpreter shell. However, take a close look at the output above. We can see a .asp file named metasploit28857905 exists on the target system at this very moment. Once the Meterpreter shell is obtained, as mentioned before, it will reside within memory. Therefore, the file is not needed, and removal was attempted by msfconsole, which failed due to access permissions. Leaving traces like these is not beneficial to the attacker and creates a huge liability. From the sysadmin’s perspective, finding files that match this name type or slight variations of it can prove beneficial to stopping an attack in the middle of its tracks. Targeting regex matches against filenames or signatures as above will not even allow an attacker to spawn a Meterpreter shell before being cut down by the correctly configured security measures. We proceed further with our exploits. Upon attempting to see which user we are running on, we get an access denied message. We should try migrating our process to a user with more privilege.

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Privilege Escalation with Local Exploit Suggester

We can easily decide to run the local exploit suggester module, attaching it to the currently active Meterpreter session. To do so, we background the current Meterpreter session, search for the module we need, and set the SESSION option to the index number for the Meterpreter session, binding the module to it.

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MSF - Session Handling

Running the recon module presents us with a multitude of options. Going through each separate one, we land on the ms15_051_client_copy_image entry, which proves to be successful. This exploit lands us directly within a root shell, giving us total control over the target system.

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MSF - Privilege Escalation