ID | Technique | Tactic |
---|---|---|
T1222.002 | Linux and Mac File and Directory Permissions Modification | Defense Evasion |
T1222 | File and Directory Permissions Modification | Defense Evasion |
Detection: Linux Auditd File Permissions Modification Via Chattr
Description
The following analytic detects suspicious file permissions modifications using the chattr command, which may indicate an attacker attempting to manipulate file attributes to evade detection or prevent alteration. The chattr command can be used to make files immutable or restrict deletion, which can be leveraged to protect malicious files or disrupt system operations. By monitoring for unusual or unauthorized chattr usage, this analytic helps identify potential tampering with critical files, enabling security teams to quickly respond to and mitigate threats associated with unauthorized file attribute changes.
Search
1`linux_auditd` `linux_auditd_normalized_proctitle_process`
2| rename host as dest
3| where LIKE(process_exec, "%chattr %") AND LIKE(process_exec, "% -i%")
4| stats count min(_time) as firstTime max(_time) as lastTime by process_exec proctitle normalized_proctitle_delimiter dest
5| `security_content_ctime(firstTime)`
6| `security_content_ctime(lastTime)`
7| `linux_auditd_file_permissions_modification_via_chattr_filter`
Data Source
Name | Platform | Sourcetype | Source | Supported App |
---|---|---|---|---|
Linux Auditd Execve | Linux | 'linux:audit' |
'/var/log/audit/audit.log' |
N/A |
Macros Used
Name | Value |
---|---|
linux_auditd | sourcetype="linux:audit" |
linux_auditd_file_permissions_modification_via_chattr_filter | search * |
linux_auditd_file_permissions_modification_via_chattr_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 implement this detection, the process begins by ingesting auditd data, that consist SYSCALL, TYPE, EXECVE and PROCTITLE events, which captures command-line executions and process details on Unix/Linux systems. These logs should be ingested and processed using Splunk Add-on for Unix and Linux (https://splunkbase.splunk.com/app/833), which is essential for correctly parsing and categorizing the data. The next step involves normalizing the field names to match the field names set by the Splunk Common Information Model (CIM) to ensure consistency across different data sources and enhance the efficiency of data modeling. This approach enables effective monitoring and detection of linux endpoints where auditd is deployed
Known False Positives
Administrator or network operator can use this application for automation purposes. Please update the filter macros to remove false positives.
Associated Analytic Story
Risk Based Analytics (RBA)
Risk Message | Risk Score | Impact | Confidence |
---|---|---|---|
A [$process_exec$] event occurred on host - [$dest$] to modify file permissions using the "chattr" command. | 49 | 70 | 70 |
References
Detection Testing
Test Type | Status | Dataset | Source | Sourcetype |
---|---|---|---|---|
Validation | ✅ Passing | N/A | N/A | N/A |
Unit | ✅ Passing | Dataset | /var/log/audit/audit.log |
linux:audit |
Integration | ✅ Passing | Dataset | /var/log/audit/audit.log |
linux:audit |
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: 1