The following analytic identifies child processes spawning from "mshta.exe". The search will return the first time and last time these command-line arguments were used for these executions, as well as the target system, the user, parent process "mshta.exe" and its child process.
- Type: TTP
- Product: Splunk Behavioral Analytics
- Datamodel: Endpoint_Processes
- Last Updated: 2022-02-23
- Author: Michael Haag, Splunk
- ID: f63f7e9c-9526-11ec-9fc7-acde48001122
|T1218||Signed Binary Proxy Execution||Defense Evasion|
1 2 3 4 5 6 7 | from read_ssa_enriched_events() | eval timestamp=parse_long(ucast(map_get(input_event, "_time"), "string", null)), cmd_line=lower(ucast(map_get(input_event, "process"), "string", null)), process_name=lower(ucast(map_get(input_event, "process_name"), "string", null)), process_path=ucast(map_get(input_event, "process_path"), "string", null), parent_process_name=ucast(map_get(input_event, "parent_process_name"), "string", null), event_id=ucast(map_get(input_event, "event_id"), "string", null) | where cmd_line IS NOT NULL AND process_name IS NOT NULL AND parent_process_name IS NOT NULL | where parent_process_name="mshta.exe" AND process_name="powershell.exe" OR process_name="cmd.exe" OR process_name="scrcons.exe" OR process_name="colorcpl.exe" OR process_name="msbuild.exe" OR process_name="microsoft.workflow.compiler.exe" OR process_name="searchprotocolhost.exe" OR process_name="cscript.exe" OR process_name="wscript.exe" | eval start_time=timestamp, end_time=timestamp, entities=mvappend(ucast(map_get(input_event, "dest_user_id"), "string", null), ucast(map_get(input_event, "dest_device_id"), "string", null)), body=create_map(["event_id", event_id, "cmd_line", cmd_line, "process_name", process_name, "parent_process_name", parent_process_name, "process_path", process_path]) | into write_ssa_detected_events();
The SPL above uses the following Macros:
windows_mshta_child_process_filter is a empty macro by default. It allows the user to filter out any results (false positives) without editing the SPL.
How To Implement
To successfully implement this search, you need to be ingesting logs with the process name, parent process, and command-line executions from your endpoints. If you are using Sysmon, you must have at least version 6.0.4 of the Sysmon TA.
Known False Positives
Although unlikely, some legitimate applications may exhibit this behavior, triggering a false positive.
Associated Analytic story
Kill Chain Phase
|80.0||80||100||An instance of $parent_process_name$ spawning $process_name$ was identified on endpoint $dest_device_id$ by user $dest_user_id$ attempting to access a remote destination to download an additional payload.|
Note that risk score is calculated base on the following formula:
(Impact * Confidence)/100
source | version: 1