The following analytic identifies a potential PowerShell script that captures screen images on compromised or targeted hosts. This technique was observed in the Winter-Vivern malware, which attempts to capture desktop screens using a PowerShell script and send the images to its C2 server as part of its exfiltration strategy. This TTP serves as a useful indicator that a PowerShell process may be gathering desktop screenshots from a host system, potentially signaling malicious activity.
- Type: TTP
Product: Splunk Enterprise, Splunk Enterprise Security, Splunk Cloud
- Last Updated: 2023-04-05
- Author: Teoderick Contreras, Splunk
- ID: 5e0b1936-8f99-4399-8ee2-9edc5b32e170
Kill Chain Phase
- CIS 10
1 2 3 4 5 `powershell` EventCode=4104 ScriptBlockText = "*[Drawing.Graphics]::FromImage(*" AND ScriptBlockText = "*New-Object Drawing.Bitmap*" AND ScriptBlockText = "*.CopyFromScreen*" | stats count min(_time) as firstTime max(_time) as lastTime by EventCode ScriptBlockText Computer UserID | `security_content_ctime(firstTime)` | `security_content_ctime(lastTime)` | `windows_screen_capture_via_powershell_filter`
The SPL above uses the following Macros:
windows_screen_capture_via_powershell_filter is a empty macro by default. It allows the user to filter out any results (false positives) without editing the SPL.
List of fields required to use this analytic.
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/220.127.116.11/GetDataIn/AddPowerShell#Configure_module_logging_for_PowerShell.
Known False Positives
Associated Analytic Story
|49.0||70||70||A PowerShell script was identified possibly performing screen captures on $Computer$.|
The Risk Score is calculated by the following formula: Risk Score = (Impact * Confidence/100). Initial Confidence and Impact is set by the analytic author.
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