ngen.exe File Download (Windows Event Log)

id: '35366.62196'
title: ngen.exe File Download
description: ngen.exe (Native Image Generator) is a legitimate Windows binary that
  compiles .NET assemblies into native machine code to improve application performance.
  Threat actors can abuse ngen.exe to download files. This use case detects ngen.exe
  executions with commands to download a file from a remote location. Living Off the
  Land Binary and Scripts (LOLBAS) (LOLBIN)
logic_format: Splunk
logic: '`get_endpoint_data` `get_endpoint_data_winevent` (TERM(EventCode=4688) OR
  "<EventID>4688<" OR Type=Process) "ngen.exe" | regex process_name="(?i)ngen\.exe"|
  regex process="(?i)ngen(\.exe(\"|\'')?)?\s+(\"|\'')?[A-Za-z0-9]{2,6}:\/\/[^\s]+"|
  table _time, host, user, process, process_*, parent_* | bin span=1s | stats values(*)
  as * by _time, host '
techniques:
- command-and-control:ingress tool transfer
technique_id: 
- T1105
data_category:
- Process command-line parameters
- Windows event logs
references:
- https://lolbas-project.github.io/lolbas/Binaries/Ngen/
- https://attack.mitre.org/techniques/T1105/
- https://learn.microsoft.com/en-us/dotnet/framework/tools/ngen-exe-native-image-generator