ID | Technique | Tactic |
---|---|---|
T1218.005 | Mshta | Defense Evasion |
Detection: Windows Process Writing File to World Writable Path
Description
The following analytic identifies a process writing a .txt file to a world writable path. This detection leverages data from Endpoint Detection and Response (EDR) agents, focusing on file creation events within specific directories. This activity is significant as adversaries often use such techniques to deliver payloads to a system, which is uncommon for legitimate processes. If confirmed malicious, this behavior could allow attackers to execute arbitrary code, escalate privileges, or maintain persistence within the environment, posing a significant security risk.
Search
1
2| tstats `security_content_summariesonly` count min(_time) as firstTime max(_time) as lastTime from datamodel=Endpoint.Filesystem where Filesystem.file_name=*.txt Filesystem.file_path IN ("*\\Windows\\Tasks\\*", "*\\Windows\\Temp\\*", "*\\Windows\\tracing\\*", "*\\Windows\\PLA\\Reports\\*", "*\\Windows\\PLA\\Rules\\*", "*\\Windows\\PLA\\Templates\\*", "*\\Windows\\PLA\\Reports\\en-US\\*", "*\\Windows\\PLA\\Rules\\en-US\\*", "*\\Windows\\Registration\\CRMLog\\*", "*\\Windows\\System32\\Tasks\\*", "*\\Windows\\System32\\Com\\dmp\\*", "*\\Windows\\System32\\LogFiles\\WMI\\*", "*\\Windows\\System32\\Microsoft\\Crypto\\RSA\\MachineKeys\\*", "*\\Windows\\System32\\spool\\PRINTERS\\*", "*\\Windows\\System32\\spool\\SERVERS\\*", "*\\Windows\\System32\\spool\\drivers\\color\\*", "*\\Windows\\System32\\Tasks\\Microsoft\\Windows\\RemoteApp and Desktop Connections Update\\*", "*\\Windows\\SysWOW64\\Tasks\\*", "*\\Windows\\SysWOW64\\Com\\dmp\\*", "*\\Windows\\SysWOW64\\Tasks\\Microsoft\\Windows\\PLA\\*", "*\\Windows\\SysWOW64\\Tasks\\Microsoft\\Windows\\RemoteApp and Desktop Connections Update\\*", "*\\Windows\\SysWOW64\\Tasks\\Microsoft\\Windows\\PLA\\System\\*") by Filesystem.dest, Filesystem.user, Filesystem.file_name Filesystem.file_path
3| `drop_dm_object_name("Filesystem")`
4| `security_content_ctime(firstTime)`
5| `security_content_ctime(lastTime)`
6| `windows_process_writing_file_to_world_writable_path_filter`
Data Source
Name | Platform | Sourcetype | Source | Supported App |
---|---|---|---|---|
N/A | N/A | N/A | N/A | N/A |
Macros Used
Name | Value |
---|---|
security_content_ctime | convert timeformat="%Y-%m-%dT%H:%M:%S" ctime($field$) |
windows_process_writing_file_to_world_writable_path_filter | search * |
windows_process_writing_file_to_world_writable_path_filter
is an empty macro by default. It allows the user to filter out any results (false positives) without editing the SPL.
Annotations
Default Configuration
This detection is configured by default in Splunk Enterprise Security to run with the following settings:
Setting | Value |
---|---|
Disabled | true |
Cron Schedule | 0 * * * * |
Earliest Time | -70m@m |
Latest Time | -10m@m |
Schedule Window | auto |
Creates Risk Event | False |
Implementation
The detection is based on data that originates from Endpoint Detection and Response (EDR) agents. These agents are designed to provide security-related telemetry from the endpoints where the agent is installed. To implement this search, you must ingest logs that contain the file creation event, process name, file path and, file name. These logs must be processed using the appropriate Splunk Technology Add-ons that are specific to the EDR product. The logs must also be mapped to the Filesystem
node of the Endpoint
data model. Use the Splunk Common Information Model (CIM) to normalize the field names and speed up the data modeling process.
Known False Positives
False positives may occur if legitimate software writes to these paths. Modify the search to include additional file name extensions. To enhance it further, adding a join on Processes.process_name may assist with restricting the analytic to specific process names. Investigate the process and file to determine if it is malicious.
Associated Analytic Story
Risk Based Analytics (RBA)
Risk Message | Risk Score | Impact | Confidence |
---|---|---|---|
A process wrote a file name- [$file_name$] to a world writable file path [$file_path$] on host- [$dest$]. | 25 | 50 | 50 |
References
Detection Testing
Test Type | Status | Dataset | Source | Sourcetype |
---|---|---|---|---|
Validation | ✅ Passing | N/A | N/A | N/A |
Unit | ✅ Passing | Dataset | XmlWinEventLog:Microsoft-Windows-Sysmon/Operational |
xmlwineventlog |
Integration | ✅ Passing | Dataset | XmlWinEventLog:Microsoft-Windows-Sysmon/Operational |
xmlwineventlog |
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: GitHub | Version: 2