SSH Proxy decryption disables vulnerability protection?

[grenzi]

Hello everyone,

  I'm doing some tests with decryption and vulnerability protection. I configured NAT and security policies to permit ssh access to an internal ssh server from the outside and I attached a vulnerability protection profile to the policy. In the vulnerability protection profile I set an exception to block bruteforce login attacks after 2 failed attempts:

This configuration works fine and connections are reset after 2 failed login. Anyway, if I add a SSH decryption policy (SSH proxy) to this connection, the bruteforce login signature is no more triggered by the failed login attempts, so it is no more effective.

Is this an issue or is it "by design", due to the fact that the firewall acts as a man in the middle for the ssh connections?

[mivaldi]

That's an interesting find. Please open a case with Support.

[grenzi]

I opened a case with the support and they confirmed this issue. Waiting for their research and feedback.

Thanks.

[grenzi]

The engineering team confirmed that this is an expected behavior. This is their explanation:

In case SSH-proxy is enabled, the signature 31914 will act on decrypted traffic. Hence, this sig will not trigger because it can not detect the pattern of the failed authentication in the decrypted traffic.

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