Powershell Fileless Script Contains Base64 Encoded Content

Powershell Fileless Script Contains Base64 Encoded Content

Description

The following analytic utilizes PowerShell Script Block Logging (EventCode=4104) to identify suspicious PowerShell execution. Script Block Logging captures the command sent to PowerShell, the full command to be executed. Upon enabling, logs will output to Windows event logs. Dependent upon volume, enable on critical endpoints or all. \ This analytic identifies FromBase64String within the script block. A typical malicious instance will include additional code. \ Command example - [Byte[]]$var_code = [System.Convert]::FromBase64String(38uqIyMjQ6rG.... \ During triage, review parallel processes using an EDR product or 4688 events. It will be important to understand the timeline of events around this activity. Review the entire logged PowerShell script block.

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Powershell Fileless Script Contains Base64 Encoded Content Help

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#ConfiguremoduleloggingforPowerShell.

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