DLL Called with Uncommon Function (Windows Event Log)

id: '27059.49379'
title: DLL Called with Uncommon Function
description: DLLs can invoke a variety of functions when executed. While these functions
  are part of legitimate Windows operations, their execution from a DLL file, especially
  in an unusual context, can be indicative of malicious behavior. Threat actors including
  Qbot have been observed abusing this technique when calling DLLs with rundll32.exe.
  This use case detects calls of uncommon functions from DLL files, accounting for
  instances where rundll32.exe has been renamed. While these function calls may be
  legitimate, unexpected executions should be investigated. 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) ".dll" ("RS32" OR "VirtualAllocEx" OR "NtUnmapViewOfSection"
  OR "CreateRemoteThread" OR "RtlCreateUserThread" OR "DeviceIoControl" OR "WriteProcessMemory"
  OR "CryptEncrypt" OR "CryptDecrypt" OR "RegSetValueEx" OR "SetWindowsHookEx" OR
  "DLLRegisterServer") | rex field=process "\.dll,(?<called_function>[^\s]+)"| where
  match(process, "(?i)\.dll\,(RS32|VirtualAllocEx|NtUnmapViewOfSection|CreateRemoteThread|RtlCreateUserThread|DeviceIoControl|WriteProcessMemory|CryptEncrypt|CryptDecrypt|RegSetValueEx|SetWindowsHookEx|DLLRegisterServer)")
  | table _time, host, user, process, process_*, parent_process, parent_process_*,
  called_function | bin span=1s | stats values(*) as * by _time, host '
techniques:
- defense-evasion:system binary proxy execution:rundll32
technique_id:
- T1218.011
data_category:
- Process command-line parameters
- Windows event logs
references:
- https://redcanary.com/blog/lolbins-abuse/