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MediumSplunk security contentTeoderick Contreras +2

Windows Change File Association Command To Notepad

The following analytic detects attempts to change the command value of a file association of an extension to open with Notepad.exe. It leverages data from Endpoint Detection and Response (EDR) agents, focusing on…

Description

The following analytic detects attempts to change the command value of a file association of an extension to open with Notepad.exe. It leverages data from Endpoint Detection and Response (EDR) agents, focusing on specific command-line patterns and registry modifications. This activity is significant as it can indicate an attempt to manipulate file handling behavior, a technique observed in APT and ransomware attacks like Prestige. After changing the extension of all encrypted files to a new one, Prestige ransomware modifies the file association for that extension to open with Notepad.exe in order to display a ransom note.

Detection logic

Detection requirements

Platform
Windows

The rule states no platform. This is derived from the ATT&CK technique it maps to.

Log source category
crowdstrike_processrollup2sysmon_eventid_1windows_event_log_security_4688

Known benign triggers

  • No false positives have been identified at this time.

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