Name:PowerShell Script Block With URL Chain id:4a3f2a7d-6402-4e64-a76a-869588ec3b57 version:3 date:2024-09-30 author:Steven Dick status:production type:TTP Description:The following analytic identifies suspicious PowerShell script execution via EventCode 4104 that contains multiple URLs within a function or array. It leverages PowerShell operational logs to detect script blocks with embedded URLs, often indicative of obfuscated scripts or those attempting to download secondary payloads. This activity is significant as it may signal an attempt to execute malicious code or download additional malware. If confirmed malicious, this could lead to code execution, further system compromise, or data exfiltration. Review parallel processes and the full script block for additional context and related artifacts. Data_source:
-Powershell Script Block Logging 4104
search:`powershell` EventCode=4104 ScriptBlockText IN ("*http:*","*https:*") | regex ScriptBlockText="(\"?(https?:\/\/(?:www\.)?[-a-zA-Z0-9@:%._\+~#=]{1,256}\.[a-zA-Z0-9()]{1,6}\b(?:[-a-zA-Z0-9()@:%_\+.~#?&\/=]*))\"?(?:,|\))?){2,}" | rex max_match=20 field=ScriptBlockText "(?<url>https?:\/\/(?:www\.)?[-a-zA-Z0-9@:%._\+~#=]{1,256}\.[a-zA-Z0-9()]{1,6}\b(?:[-a-zA-Z0-9()@:%_\+.~#?&\/=]*))" | eval Path = case(isnotnull(Path),Path,true(),"unknown") | stats count min(_time) as firstTime max(_time) as lastTime list(ScriptBlockText) as command values(Path) as file_name values(UserID) as user values(url) as url dc(url) as url_count by ActivityID, Computer, EventCode | rename Computer as dest, EventCode as signature_id | `security_content_ctime(firstTime)` | `security_content_ctime(lastTime)` | `powershell_script_block_with_url_chain_filter`
how_to_implement:The following analytic requires PowerShell operational logs to be imported. Modify the powershell macro as needed to match the sourcetype or add index. This analytic is specific to 4104, or PowerShell Script Block Logging. known_false_positives:Unknown, possible custom scripting. References: -https://www.mandiant.com/resources/blog/tracking-evolution-gootloader-operations -https://thedfirreport.com/2022/05/09/seo-poisoning-a-gootloader-story/ -https://attack.mitre.org/techniques/T1059/001/ drilldown_searches: name:'View the detection results for - "$dest$" and "$user$"' search:'%original_detection_search% | search dest = "$dest$" user = "$user$"' earliest_offset:'$info_min_time$' latest_offset:'$info_max_time$' name:'View risk events for the last 7 days for - "$dest$" and "$user$"' search:'| from datamodel Risk.All_Risk | search normalized_risk_object IN ("$dest$", "$user$") 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: - 'Malicious PowerShell' asset_type:Endpoint confidence:80 impact:100 message:A suspicious powershell script used by $user$ on host $dest$ contains $url_count$ URLs in an array, this is commonly used for malware. mitre_attack_id: - 'T1059.001' - 'T1105' observable: name:'dest' type:'Endpoint' - role: - 'Victim' name:'user' type:'User' - role: - 'Victim' name:'file_name' type:'File Name' - role: - 'Attacker' name:'url' type:'URL String' - role: - 'Attacker' product: - 'Splunk Enterprise' - 'Splunk Enterprise Security' - 'Splunk Cloud' required_fields: - '_time' - 'EventCode' - 'ActivityID' - 'Computer' - 'ScriptBlockText' risk_score:80 security_domain:endpoint
