Quser.exe Used For
Sourn Sanneh
Unfortunately this is not a console application, rather a PowerShell script that is installed as a service. The service runs as LocalSystem (not LocalService). When the service attempts to run this code it outputs the following error:
The term 'C:\Windows\system32\quser.exe' is not recognized as the name of a cmdlet, function, script file, or operable program. Check the spelling of the name, or if a path was included, verify that the path is correct and try again.
I contacted Sapien support and was informed that A service runs with no profile and does not have execution access to the system folders. You need to give the service account execution access to the exe and its support DLLs as well as using the full path to the EXE.
Quser.exe is a command line tool provided by Microsoft Windows for managing user sessions on a local or remote computer.
It allows administrators to view information about active user sessions, including the username, session ID, state, and idle time. Additionally, quser.exe can be used to disconnect or log off specific user sessions, providing administrators with the ability to manage user access to a system.
This tool is useful for system administrators who need to monitor and control user sessions on Windows-based systems, especially in a networked environment where multiple users may be connected simultaneously.
How do we know? Our SpyShelter cybersecurity labs focuses on monitoring different types of Windows PC executables and their behaviors for our popular SpyShelter Antispyware software. Learn more about us, and how our cybersecurity team studies Windows PC executables/processes.
The publisher of an executable is the entity responsible for its distribution and authenticity. Most processes/executables on your PC should be signed. The signature on the executable should have been verified through a third party whose job it is to make sure the entity is who it says it is. Find an unsigned executable? You should consider scanning any completely unsigned .exe on your PC.
Note that the OU is specified in this example as a canonical name, so can be copied and pasted out of the properties tab for an OU in AD Users and Computers rather than you having to write it in distinguished name form, although it will accept that format too. It can take a -group option instead of -ou and will recursively enumerate the given group to find all computers and the -name option can be used with both -ou and -group to further restrict what machines are interrogated.
The script is available on GitHub here and use of it is entirely at your own risk although if you run it with the -noprofile option it will not give the OK and Cancel buttons so logoff cannot be initiated from the script. It requires a minimum of version 3.0 of PowerShell, access to the Active Directory PowerShell module and pulls data from servers from 2008R2 upwards.
this does seem to be a common topic for Powershellers. I wrote something a long time ago that used CIM and the same Win32_ComputerSystem class to pull the logged on user. Something like this inside a try/catch:
The following analytic detects the execution of the Windows OS tool quser.exe, commonly used to gather information about user sessions on a Remote Desktop Session Host server. This detection leverages data from Endpoint Detection and Response (EDR) agents, focusing on process execution logs. Monitoring this activity is crucial as quser.exe is often abused by post-exploitation tools like winpeas, used in ransomware attacks to enumerate user sessions. If confirmed malicious, attackers could leverage this information to further compromise the system, maintain persistence, or escalate privileges.
The detection is based on data that originates from Endpoint Detection and Response (EDR) agents. These agents are designed to provide security-related telemetry from the endpoints where the agent is installed. To implement this search, you must ingest logs that contain the process GUID, process name, and parent process. Additionally, you must ingest complete command-line executions. These logs must be processed using the appropriate Splunk Technology Add-ons that are specific to the EDR product. The logs must also be mapped to the Processes node of the Endpoint data model. Use the Splunk Common Information Model (CIM) to normalize the field names and speed up the data modeling process.
According to a couple of articles that i have found, the quser command should exist on Windows 7, however I have a system running Windows 7 Home Premium and the QUser command does not exist in C:\windows\system32. Is there any way I can get this executable added?
You will also need to copy the quser.exe.mui file from the C:\Windows\System32\en-US folder to the same location. If you aren't using en-US as your primary locale, you will need to copy if from your current one.
I'm not an expert on software licensing but I'm guessing that any solution involving copying system files from a more expensive version of Windows lies somewhere between a violation of license terms and unsupported behavior that might break on any Windows update.
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Note: This joint Cybersecurity Advisory (CSA) is part of an ongoing #StopRansomware effort to publish advisories for network defenders that detail various ransomware variants and ransomware threat actors. These #StopRansomware advisories include recently and historically observed tactics, techniques, and procedures (TTPs) and indicators of compromise (IOCs) to help organizations protect against ransomware. Visit stopransomware.gov to see all #StopRansomware advisories and learn more about other ransomware threats and no-cost resources.
The Federal Bureau of Investigation (FBI), Cybersecurity and Infrastructure Security Agency (CISA), and Australian Cyber Security Centre (ACSC) are releasing this joint Cybersecurity Advisory to disseminate known BianLian ransomware and data extortion group IOCs and TTPs identified through FBI and ACSC investigations as of March 2023.
FBI, CISA, and ACSC encourage critical infrastructure organizations and small- and medium-sized organizations to implement the recommendations in the Mitigations section of this advisory to reduce the likelihood and impact of BianLian and other ransomware incidents.
BianLian group actors gain initial access to networks by leveraging compromised Remote Desktop Protocol (RDP) credentials likely acquired from initial access brokers [T1078],[T1133] or via phishing [T1566].
BianLian group actors use PowerShell [T1059.001] and Windows Command Shell [T1059.003] to disable antivirus tools [T1562.001], specifically Windows defender and Anti-Malware Scan Interface (AMSI). BianLian actors modify the Windows Registry [T1112] to disable tamper protection for Sophos SAVEnabled, SEDEenabled, and SAVService services, which enables them to uninstall these services. See Appendix: Windows PowerShell and Command Shell Activity for additional information, including specific commands they have used.
BianLian group uses valid accounts for lateral movement through the network and to pursue other follow-on activity. To obtain the credentials, BianLian group actors use Windows Command Shell to find unsecured credentials on the local machine [T1552.001]. FBI also observed BianLian harvest credentials from the Local Security Authority Subsystem Service (LSASS) memory [T1003.001], download RDP Recognizer (a tool that could be used to brute force RDP passwords or check for RDP vulnerabilities) to the victim system, and attempt to access an Active Directory domain database (NTDS.dit) [T1003.003].
In one case, FBI observed BianLian actors use a portable executable version of an Impacket tool (secretsdump.py) to move laterally to a domain controller and harvest credential hashes from it. Note: Impacket is a Python toolkit for programmatically constructing and manipulating network protocols. Through the Command Shell, an Impacket user with credentials can run commands on a remote device using the Windows management protocols required to support an enterprise network. Threat actors can run portable executable files on victim systems using local user rights, assuming the executable is not blocked by an application allowlist or antivirus solution.
BianLian group actors search for sensitive files using PowerShell scripts (See Appendix: Windows PowerShell and Command Shell Activity) and exfiltrate them for data extortion. Prior to January 2023, BianLian actors encrypted files [T1486] after exfiltration for double extortion.
BianLian group uses File Transfer Protocol (FTP) [T1048] and Rclone, a tool used to sync files to cloud storage, to exfiltrate data [T1537]. FBI observed BianLian group actors install Rclone and other files in generic and typically unchecked folders such as programdata\vmware and music folders. ACSC observed BianLian group actors use Mega file-sharing service to exfiltrate victim data [T1567.002].
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