Name:Linux Auditd Data Transfer Size Limits Via Split Syscall id:c03d4a49-cf9d-435b-86e9-c6f8c9b6c42e version:2 date:2024-09-30 author:Teoderick Contreras, Splunk status:production type:Anomaly Description:The following analytic detects suspicious data transfer activities that involve the use of the `split` syscall, potentially indicating an attempt to evade detection by breaking large files into smaller parts. Attackers may use this technique to bypass size-based security controls, facilitating the covert exfiltration of sensitive data. By monitoring for unusual or unauthorized use of the `split` syscall, this analytic helps identify potential data exfiltration attempts, allowing security teams to intervene and prevent the unauthorized transfer of critical information from the network. Data_source:
-Linux Auditd Syscall
search:`linux_auditd` type=SYSCALL comm=split OR exe= "*/split" | rename host as dest | stats count min(_time) as firstTime max(_time) as lastTime by comm exe SYSCALL UID ppid pid success dest | `security_content_ctime(firstTime)` | `security_content_ctime(lastTime)`| `linux_auditd_data_transfer_size_limits_via_split_syscall_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://www.splunk.com/en_us/blog/security/deep-dive-on-persistence-privilege-escalation-technique-and-detection-in-linux-platform.html 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: - 'Linux Living Off The Land' - 'Linux Privilege Escalation' - 'Linux Persistence Techniques' - 'Compromised Linux Host' asset_type:Endpoint confidence:50 impact:50 message:A SYSCALL - [$comm$] event was executed on host - [$dest$] that limits the size of data transfer. mitre_attack_id: - 'T1030' observable: name:'dest' type:'Endpoint' - role: - 'Victim' product: - 'Splunk Enterprise' - 'Splunk Enterprise Security' - 'Splunk Cloud' required_fields: - '_time' - 'comm' - 'exe' - 'SYSCALL' - 'UID' - 'ppid' - 'pid' risk_score:25 security_domain:endpoint
