Clear Unallocated Sector Using Cipher App
Description
this search is to detect execution of cipher.exe
to clear the unallocated sectors of a specific disk. This technique was seen in some ransomware to make it impossible to forensically recover deleted files.
- Type: TTP
- Product: Splunk Behavioral Analytics
- Datamodel: Endpoint_Processes
- Last Updated: 2021-12-20
- Author: Teoderick Contreras, Splunk
- ID: 8f907d90-6173-11ec-9c23-acde48001122
ATT&CK
ID | Technique | Tactic |
---|---|---|
T1070.004 | File Deletion | Defense Evasion |
T1070 | Indicator Removal on Host | Defense Evasion |
Search
1
2
3
4
5
6
| 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, "%/w:%") AND process_name="cipher.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();
Macros
The SPL above uses the following Macros:
Note that clear_unallocated_sector_using_cipher_app_filter
is a empty macro by default. It allows the user to filter out any results (false positives) without editing the SPL.
Required field
- _time
- Processes.dest
- Processes.user
- Processes.parent_process_name
- Processes.parent_process
- Processes.original_file_name
- Processes.process_name
- Processes.process
- Processes.process_id
- Processes.parent_process_path
- Processes.process_path
- Processes.parent_process_id
How To Implement
To successfully implement this search you need to be ingesting information on process that include the name of the process responsible for the changes from your endpoints into the Endpoint
datamodel in the Processes
node.
Known False Positives
administrator may execute this app to manage disk
Associated Analytic story
Kill Chain Phase
- Exploitation
RBA
Risk Score | Impact | Confidence | Message |
---|---|---|---|
90.0 | 90 | 100 | An instance of $parent_process_name$ spawning $process_name$ was identified on endpoint $dest$ by user $user$ attempting to clear the unallocated sectors of a specific disk. |
Note that risk score is calculated base on the following formula: (Impact * Confidence)/100
Reference
- https://unit42.paloaltonetworks.com/vatet-pyxie-defray777/3/
- https://www.sophos.com/en-us/medialibrary/PDFs/technical-papers/sophoslabs-ransomware-behavior-report.pdf
Test Dataset
Replay any dataset to Splunk Enterprise by using our replay.py
tool or the UI.
Alternatively you can replay a dataset into a Splunk Attack Range
source | version: 1