As a red team member, your job is to simulate real-world attacks and assess an organization’s security posture. One of the most effective ways to do this is by using remote execution techniques to gain access to systems and exfiltrate data. Remote execution is a way to execute code or commands on a remote system without physically being there. This article will focus on using sc.exe on Windows for remote execution.
What is sc.exe?
Sc.exe is a command-line tool included with Windows. It stands for Service Control Manager and is used to manage services on a local or remote system. It can start, stop, pause, modify, or create a service.
Why is sc.exe helpful for remote execution?
Sc.exe is helpful for remote execution because it can start and stop services on a remote system. When creating a new service, you can specify the executable that the service should run and then start the service remotely. This allows you to execute code on a remote system without uploading a file or executing a command directly.
How to use sc.exe for remote execution
In order to use sc.exe for remote execution, you will need to have administrative access to the remote system and sc.exe installed on your local system. Sc.exe is included with Windows, so it should already be installed.
Step 1: Create a payload
The first step in using sc.exe for remote execution is to create a payload. The payload is the code or command you want to execute on the remote system. You can use any code or command, but for the purposes of this article, we will use a simple command that will display a message box on the remote system.
The command that we will use is:
msg * "Remote Execution Successful!"
This command will display a message box on the remote system that says, “Remote Execution Successful!”.
Step 2: Encode the payload
The next step is to encode the payload and include it in the command we will use to create the new service. You can use many different encoding techniques, but for this article, we will use base64 encoding.
To encode the payload, you can use the following command:
echo msg * "Remote Execution Successful!" | certutil -encode -a -stdin output.txt
This command will encode the payload and save it to “output.txt.”
Step 3: Copy the encoded payload to the remote system
The next step is to copy the encoded payload to the remote system. There are many different ways to do this, but for this article, we will use the built-in Windows command “net use” to map a network drive to the remote system.
To map a network drive, you can use the following command:
net use Z: \\RemoteSystemName\c$ /user:Administrator Password
This command will map the C drive on the remote system to the Z drive on your local system. You will need to replace “RemoteSystemName” with the remote system’s name or IP address and “Administrator” and “Password” with the appropriate credentials.
Once you have mapped the network drive, you can copy the encoded payload to the remote system using the following command:
copy output.txt Z:\Windows\System32\
This command will copy the encoded payload to the System32 folder on the remote system.
Step 4: Create a new service
The next step is creating a new service on the remote system to execute the encoded payload. To do this, you can use the following command:
Path="C:\Windows\System32\cmd.exe /c start cmd.exe /k base64 -d output.txt" DisplayName="NewService" start=auto
This command will create a new service called “NewService” on the remote system.
The “binPath” parameter specifies the executable that the service should run,
which in this case is “cmd.exe” with the arguments /c start cmd.exe /k base64 -d output.txt. This will start a new instance of cmd.exe and run the base64 -d command to decode the payload we copied to the System32 folder.
The “displayName” parameter specifies the service’s name as it will appear in the Service Control Manager, and the “start” parameter specifies that the service should start automatically when the system boots.
Step 5: Start the new service
The final step is to start the new service on the remote system. To do this, you can use the following command:
sc start NewService
This command will start the “NewService” on the remote system, executing the encoded payload we copied to the System32 folder.
Implications
While sc.exe can be a valuable capability for red team members to perform remote execution and simulate real-world attacks, it is essential to note its limitations and implications. Firstly, sc.exe is a legitimate tool included with Windows, making it difficult to detect malicious use of the tool. This highlights the importance of effective detection and logging mechanisms to monitor for suspicious activity and identify potential security incidents. Secondly, using sc.exe requires administrative access to the remote system, which may only sometimes be feasible or practical in a real-world scenario. Finally, sc.exe can be used to create new services, modify existing services, and stop services, making it difficult to determine whether the tool is being used for legitimate or malicious purposes. As such, organizations need to monitor sc.exe and other similar tools to identify potential security incidents and respond accordingly.
Conclusion
Using sc.exe for remote execution is a powerful technique that red team members can use to access systems and exfiltrate data. By creating a new service and specifying the executable that the service should run, you can execute code on a remote system without uploading a file or executing a command directly. However, attackers can also use sc.exe to execute malicious code on a system, so organizations must monitor suspicious activity and implement security controls to prevent unauthorized access.
As a red team member, it is important to always adhere to ethical guidelines and obtain proper authorization before testing. Remote execution techniques should only be used in controlled environments with the appropriate permissions and safeguards.