Powershell Processing Stream Of Data

Name:Powershell Processing Stream Of Data
id:0d718b52-c9f1-11eb-bc61-acde48001122
version:19
date:None
author:Teoderick Contreras, Splunk
status:production
type:Anomaly
Description:The following analytic detects suspicious PowerShell script execution involving compressed stream data processing, identified via EventCode 4104. It leverages PowerShell Script Block Logging to flag scripts using `IO.Compression`, `IO.StreamReader`, or decompression methods. This activity is significant as it often indicates obfuscated PowerShell or embedded .NET/binary execution, which are common tactics for evading detection. If confirmed malicious, this behavior could allow attackers to execute hidden code, escalate privileges, or maintain persistence within the environment.
Data_source:

• -Powershell Script Block Logging 4104

search:`powershell`
EventCode=4104
ScriptBlockText IN (
"*IO.Compression.*",
"*IO.StreamReader*",
"*]::Decompress*"
)
| fillnull
| stats count min(_time) as firstTime
max(_time) as lastTime
by dest signature signature_id
user_id vendor_product EventID
Guid Opcode Name
Path ProcessID ScriptBlockId
ScriptBlockText

| `security_content_ctime(firstTime)`

| `security_content_ctime(lastTime)`

| `powershell_processing_stream_of_data_filter`

how_to_implement:To successfully implement this analytic, you will need to enable PowerShell Script Block Logging on some or all endpoints. Additional setup here https://help.splunk.com/en/security-offerings/splunk-user-behavior-analytics/get-data-in/5.4.1/add-other-data-to-splunk-uba/configure-powershell-logging-to-see-powershell-anomalies-in-splunk-uba.
known_false_positives:powershell may used this function to process compressed data.
References:
  -https://medium.com/@ahmedjouini99/deobfuscating-emotets-powershell-payload-e39fb116f7b9
  -https://help.splunk.com/en/security-offerings/splunk-user-behavior-analytics/get-data-in/5.4.1/add-other-data-to-splunk-uba/configure-powershell-logging-to-see-powershell-anomalies-in-splunk-uba
  -https://blog.palantir.com/tampering-with-windows-event-tracing-background-offense-and-defense-4be7ac62ac63
  -https://static1.squarespace.com/static/552092d5e4b0661088167e5c/t/59c1814829f18782e24f1fe2/1505853768977/Windows+PowerShell+Logging+Cheat+Sheet+ver+Sept+2017+v2.1.pdf
  -https://www.crowdstrike.com/blog/investigating-powershell-command-and-script-logging/
  -https://www.splunk.com/en_us/blog/security/hunting-for-malicious-powershell-using-script-block-logging.html
  -https://thedfirreport.com/2023/05/22/icedid-macro-ends-in-nokoyawa-ransomware/
drilldown_searches:
 name:'View the detection results for - "$Computer$" and "$user$"'
 search:'%original_detection_search% | search Computer = "$Computer$" user = "$user$"'
 earliest_offset:'$info_min_time$'
 latest_offset:'$info_max_time$'
 name:'View risk events for the last 7 days for - "$Computer$" and "$user$"'
 search:'| from datamodel Risk.All_Risk | search normalized_risk_object IN ("$Computer$", "$user$") | 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:['Hellcat Ransomware', 'Malicious PowerShell', 'Medusa Ransomware', 'PXA Stealer', 'Data Destruction', 'Braodo Stealer', 'AsyncRAT', 'Hermetic Wiper', 'IcedID', 'XWorm', 'MoonPeak', 'MuddyWater', 'Salat Stealer']

asset_type:Endpoint

mitre_attack_id:['T1059.001']

product:['Splunk Enterprise', 'Splunk Enterprise Security', 'Splunk Cloud']

category:endpoint

security_domain:endpoint

tags:

tests:
 name:'True Positive Test'
 attack_data:
  data: https://media.githubusercontent.com/media/splunk/attack_data/master/datasets/attack_techniques/T1059.001/powershell_script_block_logging/streamreader.log
  source: XmlWinEventLog:Microsoft-Windows-PowerShell/Operational
  sourcetype: XmlWinEventLog
 test_type:'unit'
manual_test:None