IT Was a Regex?? – Full CrowdStrike Report Released [video]

### Detailed Explanation of the Problem

The problem discussed in the video is related to a technical issue with the CrowdStrike Falcon sensor, specifically tied to a parameter mismatch in a new Inter-Process Communication (IPC) template type.

#### Key Components of the Problem:

1. *CrowdStrike Falcon Sensor:* - The sensor uses AI and machine learning models to protect customer systems by identifying and mitigating advanced threats. These models are updated regularly with new threat telemetry.

2. *IPC Template Type:* - Introduced in February 2024 with sensor version 7.1.11, the new IPC template type aimed to enhance detection of novel attack techniques, including the abuse of named pipes and other Windows inter-process communication (IPC) mechanisms.

3. *Template Type Parameters:* - The IPC template type defined 21 input parameter fields. However, the integration code that invoked the content interpreter for these template instances supplied only 20 input values.

4. *Rapid Response Content Channel File 291:* - This file delivered the new IPC template type to the sensors. Due to the parameter mismatch, the sensors received 20 input values instead of the required 21.

5. *Parameter Mismatch and Testing:* - The parameter count mismatch (only 20 provided instead of 21) evaded multiple layers of build validation and testing. This included stress testing and initial field deployments.

6. *Wildcard Matching Criteria:* - During testing and initial deployments, the use of a wildcard matching criterion for the 21st input parameter allowed the mismatch to go unnoticed. This wildcard essentially acted as a catch-all, masking the absence of the expected 21st parameter.

7. *Introduction of Non-Wildcard Matching:* - On July 19, 2024, two new IPC template instances were deployed. One of these introduced a non-wildcard matching criterion for the 21st input parameter. This change required the sensor to inspect the 21st input parameter explicitly.

8. *Failure of Content Validator:* - The content validator evaluated the new template instances under the assumption that the IPC template type would provide all 21 inputs. Due to the mismatch, the validator failed, leading to the incident.

9. *Root Cause Analysis Findings:* - The mismatch and subsequent failure were not discovered during the sensor release testing process. The error was identified only when the new non-wildcard template instances were deployed, causing the sensor to fail to process the IPC template correctly.

#### Implications and Consequences:

- *System Outage:* - Approximately 1% of Windows sensors were affected, remaining offline post-update.

- *Technical Debt and Oversight:* - The issue highlighted the importance of rigorous testing and validation, especially when dealing with complex systems that use regular expressions and other sophisticated matching criteria.

- *Mitigation and Future Prevention:* - The report and subsequent analysis would likely lead to improvements in testing protocols and more stringent validation processes to prevent similar issues in the future.

#### Conclusion:

The root cause of the issue was a parameter mismatch in the new IPC template type introduced by CrowdStrike. The mismatch evaded multiple layers of validation due to the use of wildcard matching criteria, which masked the absence of the required parameter. This incident underscores the importance of thorough testing and validation, especially when dealing with complex configurations and security systems.