Detection rules › Sigma

Potential Powershell ReverseShell Connection

Severity
high
Author
FPT.EagleEye, wagga, Nasreddine Bencherchali (Nextron Systems)
Source
upstream

Detects usage of the "TcpClient" class. Which can be abused to establish remote connections and reverse-shells. As seen used by the Nishang "Invoke-PowerShellTcpOneLine" reverse shell and other.

MITRE ATT&CK coverage

TacticTechniques
ExecutionT1059.001 Command and Scripting Interpreter: PowerShell

Event coverage

ProviderEvent IDTitle
Sysmon1Process creation

Stages and Predicates

Stage 1: all of selection_img

or:
Image|endswith: '\powershell.exe'
Image|endswith: '\pwsh.exe'
OriginalFileName: PowerShell.EXE
OriginalFileName: pwsh.dll

Stage 2: all of selection_cli

CommandLine|contains: ' Net.Sockets.TCPClient'
CommandLine|contains: '.GetStream('
CommandLine|contains: '.Write('

Indicators

Each row is a field, operator, and value that the rule matches. The corpus column counts how many other rules in the catalog look for the same combination: high numbers point to widely-used, community-vetted indicators. Blank or 1 shows that the indicator is specific to this rule.

FieldKindValues
CommandLinematch
  • Net.Sockets.TCPClient
  • .GetStream(
  • .Write(
Imageends_with
  • \powershell.exe corpus 143 (sigma 143)
  • \pwsh.exe corpus 140 (sigma 140)
OriginalFileNameeq
  • PowerShell.EXE corpus 64 (sigma 60, splunk 4)
  • pwsh.dll corpus 72 (sigma 68, splunk 4)