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Add Linux Auditd Enumeration Script Activity detection - #4380
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Behavioral/threshold analytic that detects the rapid fan-out of many distinct discovery utilities characteristic of automated enumeration scripts (LinEnum/LinPEAS/LSE) using Linux Auditd Execve, rather than single discovery commands. Maps to T1082/T1083/T1057/T1518.
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| | eval base_cmd=mvindex(split(base_cmd,"/"),-1) | ||
| | eval is_recon=if(base_cmd IN ("whoami","id","uname","hostname","hostnamectl","lsb_release","sudo","find","getcap","crontab","ps","netstat","ss","lsof","last","lastlog","w","who","arp","ip","ifconfig","route","mount","lsblk","df","dpkg","dpkg-query","rpm","getent","lsmod","modinfo","dmesg","env","uptime","aa-status","sestatus","capsh"),1,0) | ||
| | bin _time span=2m | ||
| | stats count as exec_count dc(base_cmd) as distinct_commands sum(is_recon) as recon_executions dc(eval(if(is_recon=1,base_cmd,null()))) as distinct_recon_commands values(base_cmd) as commands min(_time) as firstTime max(_time) as lastTime BY _time dest |
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When this fires on a CI or configuration-management host and an operator follows the documented service-account/parent-process allowlisting guidance, the filter cannot implement that tuning: this stats emits only _time, dest, aggregate counts, and commands, so user/uid, parent identity, and even the renamed process fields have been discarded before linux_auditd_enumeration_script_activity_filter runs. Preserve and collect those dimensions or apply the allowlist before aggregation; otherwise the only reliable mitigation offered here is suppressing the entire host.
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Fixed. The window now carries the allowlist dimensions: values(auid) as auid, values(uid) as uid, values(process) as process, and values(ppid) as parent_pids (plus dc(ppid) as distinct_parents). So the filter macro can allowlist a specific service account or parent process - e.g. a CI/config-management account - instead of being forced to suppress the whole host. Updated how_to_implement, known_false_positives, and the entity message to reference these. Pushed in 2b2abc4.
Summary
Adds a new anomaly analytic, Linux Auditd Enumeration Script Activity, that detects the behavior of automated Linux enumeration / privilege-escalation scripts (LinEnum, LinPEAS, linux-smart-enumeration, linuxprivchecker) rather than individual discovery commands.
Existing
Linux Auditd ...discovery analytics each key on a single technique/command. Those are valuable, but one command at a timewhoami,id,uname,find,crontab -l,ss -tlpnis everyday admin activity and generates noise. This analytic instead keys on the rapid fan-out of many distinct discovery utilities together in a short window on one host, which is the signature of an enumeration script and simultaneously covers T1082/T1083/T1057/T1518. It fires only when a 2-minute window per host crosses all three thresholds: high execution volume, high distinct-binary count, and a high number of distinct recon/discovery tools.Data source
Linux Auditd Execveusesexecve_commandandargc, consistent with the current auditd detections (e.g.linux_auditd_file_and_directory_discovery).Testing
type: Anomaly, tuned vialinux_auditd_enumeration_script_activity_filterfor config-management/monitoring/CI false positives (documented in known_false_positives).MITRE ATT&CK
T1082, T1083, T1057, T1518
Notes: thresholds are documented as starting points in how_to_implement; happy to adjust threshold values, the recon-utility list, or the grouping to match STRT conventions.