Reply to post: I experienced a similar NAT problem about a decade ago

Cloud load balancer snafu leads to 3D printer user printing on a stranger's kit

Rob F

I experienced a similar NAT problem about a decade ago

A security engineer installed a new Barracuda appliance at a community college. The next day I get a call out that their SBS server had crashed and no mail was being sent or received and the SBS was generally not serving requests.

When I looked at the system, the mail queue had 300k objects and I had to halt all services just to stop things crashing. I did a lot of cleanup, which I won't bore you with the details of. I then investigated wtf happened and it turned out that the Barracuda had NATd all public SMTP delivery to appear as an internal IP to the Exchange server. The problem is that the college had previously put in a SMTP relay configuration that trusted all internal IPs. Some spammers had quickly identified this and smashed it to send out their payloads. The public IP finally got blacklisted and I had to then go through the fun of getting them whitelisted through all the PBLs etc.

Security had managed to make the environment worse, but did fix it afterwards.

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