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Detection rules › Sigma

Potentially Suspicious ASP.NET Compilation Via AspNetCompiler

Severity
high
Author
Nasreddine Bencherchali (Nextron Systems)
Source
upstream

Detects execution of "aspnet_compiler.exe" with potentially suspicious paths for compilation.

MITRE ATT&CK coverage

TacticTechniques
Defense EvasionT1127 Trusted Developer Utilities Proxy Execution

Event coverage

ProviderEvent IDTitle
Sysmon1Process creation
Security-Auditing4688A new process has been created.

Stages and Predicates

Stage 1: selection

or:
CommandLine|contains: ':\Temp\'
CommandLine|contains: ':\Windows\System32\Tasks\'
CommandLine|contains: ':\Windows\Tasks\'
CommandLine|contains: ':\Windows\Temp\'
CommandLine|contains: '\AppData\Local\Roaming\'
CommandLine|contains: '\AppData\Local\Temp\'
CommandLine|contains: '\Users\Public\'
or:
Image|contains: ':\Windows\Microsoft.NET\Framework64\'
Image|contains: ':\Windows\Microsoft.NET\FrameworkArm64\'
Image|contains: ':\Windows\Microsoft.NET\FrameworkArm\'
Image|contains: ':\Windows\Microsoft.NET\Framework\'
Image|endswith: '\aspnet_compiler.exe'

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
  • :\Temp\ corpus 14 (sigma 14)
  • :\Windows\System32\Tasks\ corpus 3 (sigma 3)
  • :\Windows\Tasks\ corpus 6 (sigma 6)
  • :\Windows\Temp\ corpus 15 (sigma 15)
  • \AppData\Local\Roaming\
  • \AppData\Local\Temp\ corpus 16 (sigma 16)
  • \Users\Public\ corpus 17 (sigma 17)
Imageends_with
  • \aspnet_compiler.exe corpus 3 (sigma 3)
Imagematch
  • :\Windows\Microsoft.NET\Framework64\ corpus 3 (sigma 3)
  • :\Windows\Microsoft.NET\FrameworkArm64\ corpus 3 (sigma 3)
  • :\Windows\Microsoft.NET\FrameworkArm\ corpus 3 (sigma 3)
  • :\Windows\Microsoft.NET\Framework\ corpus 3 (sigma 3)

Neighbors

Broader alternatives (more inclusive than this rule)

These rules match a superset of what this rule catches. They cover the same events plus more. Use them if you want wider coverage and can absorb more false positives.