Detecting Sysmon on the Victim Host

Exploring ways to detect Sysmon presence on the victim system

Processes

attacker@victim

PS C:\> Get-Process | Where-Object { $_.ProcessName -eq "Sysmon" }

Note: process name can be changed during installation

Services

attacker@victim

Get-CimInstance win32_service -Filter "Description = 'System Monitor service'"
# or
Get-Service | where-object {$_.DisplayName -like "*sysm*"}

Note: display names and descriptions can be changed

Windows Events

attacker@victim

reg query HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\WINEVT\Channels\Microsoft-Windows-Sysmon/Operational

Filters

attacker@victim

PS C:\> fltMC.exe

Note how even though you can change the sysmon service and driver names, the sysmon altitude is always the same - 385201

Sysmon Tools + Accepted Eula

attacker@victim

ls HKCU:\Software\Sysinternals

Sysmon -c

Once symon executable is found, the config file can be checked like so:

sysmon -c

Config File on the Disk

If you are lucky enough, you may be able to find the config file itself on the disk by using native windows utility findstr:

attcker@victim

findstr /si '<ProcessCreate onmatch="exclude">' C:\tools\*

Get-SysmonConfiguration

A powershell tool by @mattifestation that extracts sysmon rules from the registry:

attacker@victim

PS C:\tools> (Get-SysmonConfiguration).Rules

As an example, looking a bit deeper into the ProcessCreate rules:

attacker@victim

(Get-SysmonConfiguration).Rules[0].Rules

We can see the rules almost as they were presented in the sysmon configuration XML file:

A snippet from the actual sysmonconfig-export.xml file:

Bypassing Sysmon

Since Get-SysmonConfiguration gives you the ability to see the rules sysmon is monitoring on, you can play around those.

Another way to bypass the sysmon altogether is explored here:

Unloading Sysmon Driver

References

Operating Offensively Against SysmonShell is Only the Beginning

PSSysmonTools/PSSysmonTools/Code/SysmonRuleParser.ps1 at master · mattifestation/PSSysmonToolsGitHub

Allocated Filter Altitudes - Windows driversMicrosoftLearn

GitHub - GhostPack/Seatbelt: Seatbelt is a C# project that performs a number of security oriented host-survey "safety checks" relevant from both offensive and defensive security perspectives.GitHub