Detecting Possible Software Intrusion in FortiGate: Understanding Digital Signature Failures

Detecting Possible Software Intrusion in FortiGate: Understanding Digital Signature Failures

In the cybersecurity landscape, ensuring the integrity of your devices is paramount. FortiGate firewalls, known for their robust security features, rely heavily on digital signatures to verify the authenticity and integrity of their firmware and updates. A failure in these signatures can be alarming and could indicate a potential software intrusion or compromise. Here’s how to detect and respond to such situations effectively.

Steps to Detect and Investigate Possible Intrusions

BIOS-Level Signature and File Integrity Checking

FortiGate devices incorporate BIOS-level signature and file integrity checking to ensure that only authenticated and untampered firmware and engine files are executed. This security feature works as follows:

• During firmware or file upload, the system verifies digital signatures signed by both Fortinet’s Certificate Authority (CA) and a third-party CA.
• During the boot process, the BIOS validates each file’s hash against its certificate.

BIOS Security Levels:

• Level 2: Enforces strict verification of both Fortinet and third-party CA signatures. Only authenticated files are permitted.
• Level 1: Allows files with valid Fortinet CA signatures but issues warnings for missing third-party validation.
• Level 0: Disables verification and is not recommended.

CLI Command:

• Check the BIOS security level and firmware signature status:

  get system status

  Example output:

  Version: FortiGate-101F v7.4.0,build2352,230427 (GA.F)
  Security Level: 0
  Firmware Signature: un-certified

Validate with Fortinet Support

• Engage Fortinet support immediately if a digital signature fails, as this could indicate either a genuine update issue or an unexpected attack.
• Provide logs and details for further analysis. Fortinet can confirm if the issue stems from a genuine error or potential compromise.

Final Thoughts

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A digital signature failure in FortiGate is a serious event that warrants immediate attention. While it may not always indicate a compromise, treating it with caution ensures the security and integrity of your network. By following best practices and engaging with Fortinet support when in doubt, you can mitigate risks and maintain a resilient cybersecurity posture.

Stay vigilant, and ensure your FortiGate devices remain secure against potential threats.