Description

On July 19, 2024, at 04:09 UTC, CrowdStrike released a sensor configuration update to Windows systems as part of the ongoing protection mechanisms of the Falcon platform. This update, however, triggered a logic error that caused system crashes and blue screens (BSOD) on impacted systems. The issue was quickly identified and remediated by 05:27 UTC the same day. This problem was not the result of a cyberattack. The affected systems were those running Falcon sensor for Windows version 7.11 and above, which were online between 04:09 UTC and 05:27 UTC on July 19, 2024. Systems that received the updated configuration during this period were prone to crashes. The sensor configuration files involved, known as “Channel Files,” are part of the Falcon sensor’s behavioral protection mechanisms. Updates to these files occur several times a day in response to new tactics and techniques identified by CrowdStrike. This process has been in place since Falcon’s inception. On Windows systems, Channel Files are located in the following directory: **C:\Windows\System32\drivers\CrowdStrike\** The files have names starting with “C-” followed by a unique identifier number. The specific Channel File implicated in this event is 291, with filenames starting with “C-00000291-” and ending with a .sys extension. Despite the .sys extension, these Channel Files are not kernel drivers. Channel File 291 manages how Falcon assesses named pipe execution on Windows systems. Named pipes are used for interprocess or intersystem communication in Windows. The update released at 04:09 UTC aimed to target malicious named pipes used by common C2 frameworks. However, it triggered a logic error, causing system crashes. CrowdStrike corrected this by updating Channel File 291, without making additional changes. Falcon continues to protect against named pipe abuse. This issue was not related to null bytes in Channel File 291 or any other file.