Name:Linux Auditd At Application Execution id:9f306e0a-1c36-469e-8892-968ca12470dd version:5 date:2025-02-20 author:Teoderick Contreras, Splunk status:production type:Anomaly Description:The following analytic detects the execution of the "At" application in Linux, which can be used by attackers to create persistence entries on a compromised host. This detection leverages data from Endpoint Detection and Response (EDR) agents, focusing on process names and parent process names associated with "at" or "atd". This activity is significant because the "At" application can be exploited to maintain unauthorized access or deliver additional malicious payloads. If confirmed malicious, this behavior could lead to data theft, ransomware attacks, or other severe consequences. Immediate investigation is required to determine the legitimacy of the execution and mitigate potential risks. Data_source:
-Linux Auditd Syscall
search:`linux_auditd` type=SYSCALL comm IN ("at", "atd") OR exe IN ("/usr/bin/at","/usr/bin/atd") AND NOT (UID IN("daemon")) | rename host as dest | stats count min(_time) as firstTime max(_time) as lastTime by comm exe SYSCALL UID ppid pid dest | `security_content_ctime(firstTime)` | `security_content_ctime(lastTime)`| `linux_auditd_at_application_execution_filter`
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 use this application for automation purposes. Please update the filter macros to remove false positives. References: -https://attack.mitre.org/techniques/T1053/001/ -https://www.linkedin.com/pulse/getting-attacker-ip-address-from-malicious-linux-job-craig-rowland/ 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 ("$dest$") starthoursago=168 | 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:'$info_min_time$' latest_offset:'$info_max_time$' tags: analytic_story: - 'Scheduled Tasks' - 'Linux Privilege Escalation' - 'Linux Persistence Techniques' - 'Linux Living Off The Land' - 'Compromised Linux Host' asset_type:Endpoint mitre_attack_id: - 'T1053.002' product: - 'Splunk Enterprise' - 'Splunk Enterprise Security' - 'Splunk Cloud' security_domain:endpoint
