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Description

An attacker may use LOLBAS tools spawned from vulnerable applications not typically used by system administrators. This analytic leverages the Splunk Streaming ML DSP plugin to find rare parent/child relationships. The list of application has been extracted from https://github.com/LOLBAS-Project/LOLBAS/tree/master/yml/OSBinaries

  • Type: Anomaly
  • Product: Splunk Behavioral Analytics
  • Datamodel: Endpoint_Processes
  • Last Updated: 2021-11-30
  • Author: Peter Gael, Splunk; Ignacio Bermudez Corrales, Splunk
  • ID: cf090c78-bcc6-11eb-8529-0242ac130003

ATT&CK

ID Technique Tactic
T1203 Exploitation for Client Execution Execution
T1059 Command and Scripting Interpreter Execution
T1053 Scheduled Task/Job Execution, Persistence, Privilege Escalation
T1072 Software Deployment Tools Execution, Lateral Movement 
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| from read_ssa_enriched_events() 
| eval timestamp=parse_long(ucast(map_get(input_event, "_time"), "string", null)) 
| eval parent_process=lower(ucast(map_get(input_event, "parent_process_name"), "string", null)), parent_process_name=mvindex(split(parent_process, "\\"), -1), process_name=lower(ucast(map_get(input_event, "process_name"), "string", null)), cmd_line=ucast(map_get(input_event, "process"), "string", null), dest_user_id=ucast(map_get(input_event, "dest_user_id"), "string", null), dest_device_id=ucast(map_get(input_event, "dest_device_id"), "string", null), event_id=ucast(map_get(input_event, "event_id"), "string", null) 
| where parent_process_name!=null 
| select parent_process_name, process_name, cmd_line, timestamp, dest_device_id, dest_user_id 
| conditional_anomaly conditional="parent_process_name" target="process_name" 
| where (process_name="powershell.exe" OR process_name="regsvcs.exe" OR process_name="ftp.exe" OR process_name="dfsvc.exe" OR process_name="rasautou.exe" OR process_name="schtasks.exe" OR process_name="xwizard.exe" OR process_name="findstr.exe" OR process_name="esentutl.exe" OR process_name="cscript.exe" OR process_name="reg.exe" OR process_name="csc.exe" OR process_name="atbroker.exe" OR process_name="print.exe" OR process_name="pcwrun.exe" OR process_name="vbc.exe" OR process_name="rpcping.exe" OR process_name="wsreset.exe" OR process_name="ilasm.exe" OR process_name="certutil.exe" OR process_name="replace.exe" OR process_name="mshta.exe" OR process_name="bitsadmin.exe" OR process_name="wscript.exe" OR process_name="ieexec.exe" OR process_name="cmd.exe" OR process_name="microsoft.workflow.compiler.exe" OR process_name="runscripthelper.exe" OR process_name="makecab.exe" OR process_name="forfiles.exe" OR process_name="desktopimgdownldr.exe" OR process_name="control.exe" OR process_name="msbuild.exe" OR process_name="register-cimprovider.exe" OR process_name="tttracer.exe" OR process_name="ie4uinit.exe" OR process_name="sc.exe" OR process_name="bash.exe" OR process_name="hh.exe" OR process_name="cmstp.exe" OR process_name="mmc.exe" OR process_name="jsc.exe" OR process_name="scriptrunner.exe" OR process_name="odbcconf.exe" OR process_name="extexport.exe" OR process_name="msdt.exe" OR process_name="diskshadow.exe" OR process_name="extrac32.exe" OR process_name="eventvwr.exe" OR process_name="mavinject.exe" OR process_name="regasm.exe" OR process_name="gpscript.exe" OR process_name="rundll32.exe" OR process_name="regsvr32.exe" OR process_name="regedit.exe" OR process_name="msiexec.exe" OR process_name="gfxdownloadwrapper.exe" OR process_name="presentationhost.exe" OR process_name="regini.exe" OR process_name="wmic.exe" OR process_name="runonce.exe" OR process_name="syncappvpublishingserver.exe" OR process_name="verclsid.exe" OR process_name="psr.exe" OR process_name="infdefaultinstall.exe" OR process_name="explorer.exe" OR process_name="expand.exe" OR process_name="installutil.exe" OR process_name="netsh.exe" OR process_name="wab.exe" OR process_name="dnscmd.exe" OR process_name="at.exe" OR process_name="pcalua.exe" OR process_name="cmdkey.exe" OR process_name="msconfig.exe") 
| eval input = (-1)*log(output) 
| adaptive_threshold algorithm="gaussian" threshold=0.001 window=604800000L 
| where label AND input > mean 
| eval start_time = timestamp, end_time = timestamp, entities = mvappend(dest_device_id, dest_user_id), body = create_map(["process_name", process_name, "parent_process_name", parent_process_name, "input", input, "mean", mean, "variance", variance, "output", output, "cmd_line", cmd_line]) 
| into write_ssa_detected_events();

Macros

The SPL above uses the following Macros:

Note that rare_parent-child_process_relationship_filter is a empty macro by default. It allows the user to filter out any results (false positives) without editing the SPL.

Required field

  • process
  • process_name
  • parent_process_name
  • _time
  • dest_device_id
  • dest_user_id
  • cmd_line

How To Implement

Collect endpoint data such as sysmon or 4688 events.

Known False Positives

Some custom tools used by administrators could be used rarely to launch remotely applications. This might trigger false positives at the beginning when it has not collected yet enough data to construct the baseline.

Associated Analytic story

Kill Chain Phase

  • Exploitation

Note that risk score is calculated base on the following formula: (Impact * Confidence)/100

Reference

Test Dataset

Replay any dataset to Splunk Enterprise by using our replay.py tool or the UI. Alternatively you can replay a dataset into a Splunk Attack Range

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