The following analytics identifies the resizing of shadowstorage by ransomware malware to avoid the shadow volumes being made again. this technique is an alternative by ransomware attacker than deleting the shadowstorage which is known alert in defensive team. one example of ransomware that use this technique is CLOP ransomware where it drops a .bat file that will resize the shadowstorage to minimum size as much as possible
- Type: TTP
- Product: Splunk Behavioral Analytics
- Datamodel: Endpoint_Processes
- Last Updated: 2021-06-21
- Author: Teoderick Contreras, Splunk
- ID: dbc30554-d27e-11eb-9e5e-acde48001122
| 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 like(cmd_line, "%resize%") AND like(cmd_line, "%shadowstorage%") AND like(cmd_line, "%maxsize%") AND process_name="vssadmin.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();
Associated Analytic Story
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.
Kill Chain Phase
Known False Positives
System administrators may resize the shadowstorage for valid purposes. Filter as needed.
|64.0||80||80||An instance of $parent_process_name$ spawning $process_name$ was identified on endpoint $dest_device_id$ by user $dest_user_id$ attempting to create a shadow copy to perform offline password cracking.|
source | version: 2