This analytic looks for suspicious chmod utility execution to enable SUID bit. This allows a user to temporarily gain root access, usually in order to run a program. For example, only the root account is allowed to change the password information contained in the password database; If the SUID bit appears as an s, the file’s owner also has execute permission to the file; if it appears as an S, the file’s owner does not have execute permission. The second specialty permission is the SGID, or set group id bit. It is similar to the SUID bit, except it can temporarily change group membership, usually to execute a program. The SGID bit is set if an s or an S appears in the group section of permissions.
- Type: Anomaly
- Product: Splunk Enterprise, Splunk Enterprise Security, Splunk Cloud
- Datamodel: Endpoint
- Last Updated: 2021-12-21
- Author: Teoderick Contreras, Splunk
- ID: bf0304b6-6250-11ec-9d7c-acde48001122
Kill Chain Phase
- CIS 3
- CIS 5
- CIS 16
1 2 3 4 5 6 | tstats `security_content_summariesonly` count min(_time) as firstTime max(_time) as lastTime from datamodel=Endpoint.Processes WHERE (Processes.process_name = chmod OR Processes.process = "*chmod *") AND Processes.process IN("* g+s *", "* u+s *", "* 4777 *", "* 4577 *") by Processes.dest Processes.user Processes.parent_process_name Processes.process_name Processes.process Processes.process_id Processes.parent_process_id Processes.process_guid | `drop_dm_object_name(Processes)` | `security_content_ctime(firstTime)` | `security_content_ctime(lastTime)` | `linux_setuid_using_chmod_utility_filter`
The SPL above uses the following Macros:
linux_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.
How To Implement
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
Administrator or network operator can execute this command. Please update the filter macros to remove false positives.
Associated Analytic story
|49.0||70||70||a commandline $process$ that may set suid or sgid on $dest$|
The Risk Score is calculated by the following formula: Risk Score = (Impact * Confidence/100). Initial Confidence and Impact is set by the analytic author.
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