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Description

The following analytic detects the execution of the chmod utility to set the SUID or SGID bit on files, which can allow users to temporarily gain root or group-level access. This detection leverages data from Linux Auditd, focusing on process names and command-line arguments related to chmod. This activity is significant as it can indicate an attempt to escalate privileges or maintain persistence on a system. If confirmed malicious, an attacker could gain elevated access, potentially compromising sensitive data or critical system functions.

  • Type: Anomaly

  • Product: Splunk Enterprise, Splunk Enterprise Security, Splunk Cloud

  • Last Updated: 2024-09-04
  • Author: Teoderick Contreras, Splunk
  • ID: 8230c407-1b47-4d95-ac2e-718bd6381386

Annotations

ATT&CK

ATT&CK

ID Technique Tactic
T1548.001 Setuid and Setgid Privilege Escalation, Defense Evasion
T1548 Abuse Elevation Control Mechanism Privilege Escalation, Defense Evasion
Kill Chain Phase
  • Exploitation
NIST
  • DE.AE
CIS20
  • CIS 10
CVE 


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`linux_auditd` `linux_auditd_normalized_proctitle_process` 
| rename host as dest 
| where LIKE (process_exec, "%chmod %") AND (LIKE (process_exec, "% u+s %") OR LIKE (process_exec, "% g+s %") OR LIKE (process_exec, "% 4777 %") OR LIKE (process_exec, "% 4577 %")) 
| stats count min(_time) as firstTime max(_time) as lastTime by process_exec proctitle normalized_proctitle_delimiter dest 
| `security_content_ctime(firstTime)` 
| `security_content_ctime(lastTime)`
| `linux_auditd_setuid_using_chmod_utility_filter`

Macros

The SPL above uses the following Macros:

:information_source: linux_auditd_setuid_using_chmod_utility_filter is a empty macro by default. It allows the user to filter out any results (false positives) without editing the SPL.

Required fields

List of fields required to use this analytic.

  • _time
  • proctitle

How To Implement

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 execute this command. Please update the filter macros to remove false positives.

Associated Analytic Story

RBA

Risk Score Impact Confidence Message
81.0 90 90 A [$process_exec$] event occurred on host - [$dest$] to set the SUID or SGID bit on files using the chmod utility.

:information_source: The Risk Score is calculated by the following formula: Risk Score = (Impact * Confidence/100). Initial Confidence and Impact is set by the analytic author.

Reference

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