Name:Windows Exfiltration Over C2 Via Invoke RestMethod id:06ade821-f6fa-40d0-80af-15bc1d45b3ba version:3 date:2024-09-30 author:Teoderick Contreras, Splunk status:production type:TTP Description:The following analytic detects potential data exfiltration using PowerShell's Invoke-RestMethod. It leverages PowerShell Script Block Logging to identify scripts that attempt to upload files via HTTP POST requests. This activity is significant as it may indicate an attacker is exfiltrating sensitive data, such as desktop screenshots or files, to an external command and control (C2) server. If confirmed malicious, this could lead to data breaches, loss of sensitive information, and further compromise of the affected systems. Immediate investigation is recommended to determine the intent and scope of the activity. Data_source:
-Powershell Script Block Logging 4104
search:`powershell` EventCode=4104 ScriptBlockText = "*Invoke-RestMethod *" AND ScriptBlockText = "* -Uri *" AND ScriptBlockText = "* -Method *" AND ScriptBlockText = "* Post *" AND ScriptBlockText = "* -InFile *" | stats count min(_time) as firstTime max(_time) as lastTime by EventCode ScriptBlockText Computer UserID | `security_content_ctime(firstTime)` | `security_content_ctime(lastTime)` | `windows_exfiltration_over_c2_via_invoke_restmethod_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://docs.splunk.com/Documentation/UBA/5.0.4.1/GetDataIn/AddPowerShell#Configure_module_logging_for_PowerShell. known_false_positives:False positives should be limited. Filter as needed. References: -https://twitter.com/_CERT_UA/status/1620781684257091584 -https://cert.gov.ua/article/3761104 drilldown_searches: name:'View the detection results for - "$Computer$"' search:'%original_detection_search% | search Computer = "$Computer$"' earliest_offset:'$info_min_time$' latest_offset:'$info_max_time$' name:'View risk events for the last 7 days for - "$Computer$"' search:'| from datamodel Risk.All_Risk | search normalized_risk_object IN ("$Computer$") 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: - 'Winter Vivern' asset_type:Endpoint confidence:70 impact:70 message:A PowerShell script on $Computer$ is attempting to transfer files to a remote URL. mitre_attack_id: - 'T1041' observable: name:'Computer' type:'Hostname' - role: - 'Victim' product: - 'Splunk Enterprise' - 'Splunk Enterprise Security' - 'Splunk Cloud' required_fields: - '_time' - 'ScriptBlockText' - 'Computer' - 'UserID' - 'EventCode' risk_score:49 security_domain:endpoint
