Read the Data Communications article they provided:

PIX also increases network security. Since there's no way for anyone on the Internet to know which machine on the corporate network is using a Class C address at any given time, it's impossible to establish a telnet or FTP session with any particular device.

And what about hosts that should be recognizable from the Internet, such as mail servers? These either can be directly attached to the Internet and assigned a public address or can be attached through PIX. In the latter case, the translator is config- ured to map one of the external addresses to the device not just for the duration of an application session but on a permanent basis.

At some point you're going to have to find a way to argue that the Cisco PIX was not a security device; again: it was the flagship product of the security SBU.

I was there at the time, doing IP network engineering (for a Chicagoland ISP). The PIX was a security device, and NAT was understood as a security feature (for sure, also an address depletion feature, but the argument that's being made in the post isn't merely that it was an address depletion thing, but also that it categorically wasn't a security feature, which is just obviously false.)

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simoncion 2 hours ago | parent [-]

> At some point you're going to have to find a way to argue that the Cisco PIX was not a security device...

What? It's a firewall that can do NAT. The PIX is clearly a security device. NAT is clearly an address-depletion-mitigation technique.

> Since there's no way for anyone on the Internet to know which machine on the corporate network is using a Class C address at any given time, it's impossible to establish a telnet or FTP session with any particular device.

Right. And you can achieve the exact same effect with a firewall on an edge router or on a host. I get that firewalls might have been much less common thirty-ish years ago and that doing packet filtering might have been pretty novel for many, leading folks to get confused when they encountered a combination firewall+NAT device.

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tptacek 2 hours ago | parent [-]

I'm not sure I can be any clearer about the fact that NAT is both a security feature and an address management feature. I feel like people who weren't practitioners are the time are trying to reason axiomatically that every feature fits into precisely one bucket, or that a security feature isn't a true security feature if it can be replaced by one or more other "cleaner" security features. None of that is true. Practitioners at the time were not confused.

"You can achieve the same effect" doesn't mean anything in this discussion. If that's your argument, you've conceded the debate.

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simoncion 2 hours ago | parent [-]

Ah, I see what you're driving at.

It's a security feature in the same way that a power-cut switch is a security feature. A power-cut switch's purpose is cut power to a machine so that it can -say- be safely worked on or relocated (or simply to not draw power when the machine's not in use), the machine also happens to be inaccessible while its power is cut.

Sure. It's not technically a lie to call a power-cut switch a security feature for most pieces of kit. I'd still laugh at the salesman that made the assertion. If I were feeling particularly cunty, I'd ask him if he injured himself from that great big stretch.

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tptacek 2 hours ago | parent [-]

I can't emphasize enough how much of a retcon it is to say "it's not technically a lie" that NAT is a security feature. It was deployed in hundreds of networks specifically as a security feature, and it is part of the security posture of hundreds of thousands of home networks today. People who say "NAT isn't a security feature" are simply wrong.

There are lots of security features I personally don't like either. I don't claim they're not security features; I say they're bad security features.

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Dylan16807 an hour ago | parent [-]

The PIX evidence above doesn't make it look like a retcon. Do you have something better to show about those hundreds of networks?

	▲	kortilla 2 minutes ago \| parent [-]
		> Since there's no way for anyone on the Internet to know which machine on the corporate network is using a Class C address at any given time, it's impossible to establish a telnet or FTP session with any particular device. This is a security feature ad, nothing else. And it’s 100% because of NAT, not anything else in the PIX feature set.