Name:Linux Auditd Possible Access To Sudoers File id:8be88f46-f7e8-4ae6-b15e-cf1b13392834 version:14 date:None author:Teoderick Contreras, Nasreddine Bencherchali, Splunk status:production type:Anomaly Description:The following analytic detects potential access or modification of the /etc/sudoers file on a Linux system.
It leverages data from Linux Auditd, focusing on events of type PATH or CWD.
This activity could be significant because the sudoers file controls user permissions for executing commands with elevated privileges.
Correlate this with related EXECVE or PROCTITLE events to identify the process or user responsible for the access or modification.
If confirmed malicious, an attacker could gain persistence or escalate privileges, compromising the security of the targeted host.
Data_source:
-Linux Auditd Path
-Linux Auditd Cwd
search:`linux_auditd` (type=PATH OR type=CWD) | rex "msg=audit\([^)]*:(?<audit_id>\d+)\)"
| stats values(type) as types values(name) as names values(nametype) as nametype values(cwd) as cwd_list values(_time) as event_times by audit_id, host
| stats count min(e_time) as firstTime max(e_time) as lastTime values(nametype) as nametype by current_working_directory reconstructed_path match_count dest audit_id
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 and make sure the type=CWD record type is activate in your auditd configuration.
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.
References: -https://attack.mitre.org/techniques/T1548/003/ -https://web.archive.org/web/20210708035426/https://www.cobaltstrike.com/downloads/csmanual43.pdf drilldown_searches: name:'View the detection results for - "$dest$"' search:'%original_detection_search% | search dest = "$dest$"' earliest_offset:'$info_min_time$' latest_offset:'$info_max_time$' name:'View risk events for the last 7 days for - "$dest$"' search:'| from datamodel Risk.All_Risk | search normalized_risk_object IN ("$dest$") | stats count min(_time) as firstTime max(_time) as lastTime values(search_name) as "Search Name" values(risk_message) as "Risk Message" values(analyticstories) as "Analytic Stories" values(annotations._all) as "Annotations" values(annotations.mitre_attack.mitre_tactic) as "ATT&CK Tactics" by normalized_risk_object | `security_content_ctime(firstTime)` | `security_content_ctime(lastTime)`' earliest_offset:'7d' latest_offset:'0' analytic_story:['Linux Persistence Techniques', 'Compromised Linux Host', 'China-Nexus Threat Activity', 'Salt Typhoon', 'Linux Privilege Escalation']
