ID | Technique | Tactic |
---|---|---|
T1485 | Data Destruction | Impact |
T1070.004 | File Deletion | Defense Evasion |
T1070 | Indicator Removal | Defense Evasion |
Detection: Linux High Frequency Of File Deletion In Boot Folder
Description
The following analytic detects a high frequency of file deletions in the /boot/ folder on Linux systems. It leverages filesystem event logs to identify when 200 or more files are deleted within an hour by the same process. This behavior is significant as it may indicate the presence of wiper malware, such as Industroyer2, which targets critical system directories. If confirmed malicious, this activity could lead to system instability or failure, hindering the boot process and potentially causing a complete system compromise.
Search
1
2| tstats `security_content_summariesonly` values(Filesystem.file_name) as deletedFileNames values(Filesystem.file_path) as deletedFilePath dc(Filesystem.file_path) as numOfDelFilePath count min(_time) as firstTime max(_time) as lastTime FROM datamodel=Endpoint.Filesystem where Filesystem.action=deleted Filesystem.file_path = "/boot/*" by _time span=1h Filesystem.dest Filesystem.process_guid Filesystem.action
3| `drop_dm_object_name(Filesystem)`
4| where numOfDelFilePath >= 200
5| `security_content_ctime(firstTime)`
6| `security_content_ctime(lastTime)`
7| `linux_high_frequency_of_file_deletion_in_boot_folder_filter`
Data Source
Name | Platform | Sourcetype | Source |
---|---|---|---|
Sysmon for Linux EventID 11 | Linux | 'sysmon:linux' |
'Syslog:Linux-Sysmon/Operational' |
Macros Used
Name | Value |
---|---|
security_content_ctime | convert timeformat="%Y-%m-%dT%H:%M:%S" ctime($field$) |
linux_high_frequency_of_file_deletion_in_boot_folder_filter | search * |
linux_high_frequency_of_file_deletion_in_boot_folder_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 Notable | Yes |
Rule Title | %name% |
Rule Description | %description% |
Notable Event Fields | user, dest |
Creates Risk Event | True |
Implementation
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 can use the Add-on for Linux Sysmon from Splunkbase.
Known False Positives
linux package installer/uninstaller may cause this event. Please update you filter macro to remove false positives.
Associated Analytic Story
Risk Based Analytics (RBA)
Risk Message | Risk Score | Impact | Confidence |
---|---|---|---|
Multiple files detection in /boot/ folder on $dest$ by process GUID - $process_guid$ | 80 | 100 | 80 |
References
Detection Testing
Test Type | Status | Dataset | Source | Sourcetype |
---|---|---|---|---|
Validation | ✅ Passing | N/A | N/A | N/A |
Unit | ✅ Passing | Dataset | Syslog:Linux-Sysmon/Operational |
sysmon:linux |
Integration | ✅ Passing | Dataset | Syslog:Linux-Sysmon/Operational |
sysmon:linux |
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: 4