legitimate use of rundll32 to load log.dll from trusted locations may trigger this. allowlist known paths or parent processes as needed.

Techniques

T1574

Sample rules

Windows Rundll32 Execution With Log.DLL

source: splunk
technicques:
- T1574

Description

Identifies the execution of rundll32 with a command line argument of “log.dll”, as used in the Lotus Blossom Chrysalis backdoor campaign. Attackers placed a malicious “log.dll” in “%AppData%\Bluetooth” and invoked it via rundll32.exe “log.dll,LogInit” to decrypt and execute ShellCode. The legitimate Bitdefender Submission Wizard (BDSubmit.exe, bdsw.exe) also uses log.dll and is vulnerable to DLL sideloading.

Detection logic


| tstats `security_content_summariesonly` count min(_time) as firstTime max(_time) as lastTime
  from datamodel=Endpoint.Processes where
  `process_rundll32`
  Processes.process="* log.dll*"
  by Processes.action Processes.dest Processes.original_file_name Processes.parent_process Processes.parent_process_exec Processes.parent_process_guid Processes.parent_process_id Processes.parent_process_name Processes.parent_process_path Processes.process Processes.process_exec Processes.process_guid Processes.process_hash Processes.process_id Processes.process_integrity_level Processes.process_name Processes.process_path Processes.user Processes.user_id Processes.vendor_product

| `drop_dm_object_name(Processes)`

| `security_content_ctime(firstTime)`

| `security_content_ctime(lastTime)`

| `windows_rundll32_execution_with_log_dll_filter`