Name:Any Powershell DownloadFile id:1a93b7ea-7af7-11eb-adb5-acde48001122 version:7 date:2024-09-30 author:Michael Haag, Splunk status:production type:TTP Description:The following analytic detects the use of PowerShell's `DownloadFile` method to download files. It leverages data from Endpoint Detection and Response (EDR) agents, focusing on process execution logs. This activity is significant as it is commonly used in malicious frameworks to download and execute additional payloads. If confirmed malicious, this could lead to unauthorized code execution, data exfiltration, or further compromise of the system. Analysts should investigate the source and destination of the download and review AMSI or PowerShell transaction logs for additional context. Data_source:
-Sysmon EventID 1
-Windows Event Log Security 4688
-CrowdStrike ProcessRollup2
search:| tstats `security_content_summariesonly` count min(_time) as firstTime max(_time) as lastTime from datamodel=Endpoint.Processes where `process_powershell` Processes.process=*DownloadFile* by Processes.dest Processes.user Processes.parent_process Processes.process_name Processes.parent_process_name Processes.original_file_name Processes.process Processes.process_id Processes.parent_process_id | `drop_dm_object_name(Processes)` | `security_content_ctime(firstTime)`| `security_content_ctime(lastTime)`| `any_powershell_downloadfile_filter`
how_to_implement:The detection is based on data that originates from Endpoint Detection and Response (EDR) agents. These agents are designed to provide security-related telemetry from the endpoints where the agent is installed. To implement this search, you must ingest logs that contain the process GUID, process name, and parent process. Additionally, you must ingest complete command-line executions. These logs must be processed using the appropriate Splunk Technology Add-ons that are specific to the EDR product. The logs must also be mapped to the `Processes` node of the `Endpoint` data model. Use the Splunk Common Information Model (CIM) to normalize the field names and speed up the data modeling process. known_false_positives:False positives may be present and filtering will need to occur by parent process or command line argument. It may be required to modify this query to an EDR product for more granular coverage. References: -https://docs.microsoft.com/en-us/dotnet/api/system.net.webclient.downloadfile?view=net-5.0 -https://blog.malwarebytes.com/malwarebytes-news/2021/02/lazyscripter-from-empire-to-double-rat/ -https://github.com/redcanaryco/atomic-red-team/blob/master/atomics/T1059.001/T1059.001.md drilldown_searches: name:'View the detection results for - "$user$" and "$dest$"' search:'%original_detection_search% | search user = "$user$" dest = "$dest$"' earliest_offset:'$info_min_time$' latest_offset:'$info_max_time$' name:'View risk events for the last 7 days for - "$user$" and "$dest$"' search:'| from datamodel Risk.All_Risk | search normalized_risk_object IN ("$user$", "$dest$") 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: - 'DarkCrystal RAT' - 'Ingress Tool Transfer' - 'Hermetic Wiper' - 'Malicious PowerShell' - 'Data Destruction' - 'Log4Shell CVE-2021-44228' - 'Phemedrone Stealer' - 'Braodo Stealer' - 'PXA Stealer' asset_type:Endpoint confidence:70 cve: - 'CVE-2021-44228' impact:80 message:An instance of $parent_process_name$ spawning $process_name$ was identified on endpoint $dest$ by user $user$. This behavior identifies the use of DownloadFile within PowerShell. mitre_attack_id: - 'T1059' - 'T1059.001' - 'T1105' observable: name:'user' type:'User' - role: - 'Victim' name:'dest' type:'Hostname' - role: - 'Victim' name:'parent_process_name' type:'Process' - role: - 'Attacker' name:'process_name' type:'Process' - role: - 'Attacker' product: - 'Splunk Enterprise' - 'Splunk Enterprise Security' - 'Splunk Cloud' required_fields: - '_time' - 'Processes.dest' - 'Processes.user' - 'Processes.parent_process_name' - 'Processes.parent_process' - 'Processes.original_file_name' - 'Processes.process_name' - 'Processes.process' - 'Processes.process_id' - 'Processes.parent_process_path' - 'Processes.process_path' - 'Processes.parent_process_id' risk_score:56 security_domain:endpoint
