4 ms·

>NAT is absolutely not in any way a substitute for an actual firewall, despite the side effect of 'blocking' ports. This is one of those infosec tenets that is

>NAT is absolutely not in any way a substitute for an actual firewall, despite the side effect of 'blocking' ports. This is one of those infosec tenets that is technically true but functionally unhelpful. Like correct-horse-battery-stable debates. The claim is that IPv4 + NAT + bad firewall is better than IPv6 + bad firewall. Yes, both are insufficient and inferior to a good firewall - but how confident are you that you never interact with a bad firewall?

derefr 4y ago
What makes you think that, for critical systems, "IPv4 + NAT + bad firewall" is the default IPv4 deployment paradigm, rather than "IPV4 + bad firewall"? Sure, big IaaS providers like AWS put you in a VPC by default. But most servers on the net are not hosted in an IaaS; they're hosted using a VPS or bare-metal hosting provider, or just coloed in a DC by their owner. And in all those cases, what that kind of deployment gets you, is a public IPv4 per VM/machine, that anyone on the Internet can march right up and talk to, where it's the responsibility of the machine itself to reject incoming packets (i.e. at the OS level with a kernel firewall.) NAT on IPv4 is only really a default assumption for residential networks. Anywhere else, it's pretty much like the movie WarGames: even the mainframe has a phone number you can call. Staying on IPv4 isn't making anyone safe.
- 293984j29384 4y ago
  While I don't have any factual proof to refute your statements, in my personal experience almost every organization uses NAT & RFC1918 address space. The only client I can think of in my 20 years of experience that used a public IPv4 per VM/machine was the DoD, specifically, the U.S. Army. From your very last statement, I think you've confused self hosting (like buying a VPS from Digital Ocean and hosting your own blag) and how the real world works (like going to Dell.com and ordering a new laptop). "The mainframe" these days is almost always behind a L4/L7 load balancer or other network device and very rarely directly addressable.
  - SoftTalker 4y ago
    Big universities (at least in my experience in the USA) are the other ones that would have a public IP address for every device, at least until rather recently. They were online very early and got allocated huge blocks of addresses, before anyone really imagined future scarcity.
    - icedchai 4y ago
      In the mid-90's, every system at my university had a public IP address, including those on the campus residential networks. There were no firewalls. It was also a flat address space (/16, 255.255.0.0) for the whole campus! The 90's were certainly a different time.
  - derefr 4y ago
    My company runs an API SaaS; my impressions come from a hobby I have of looking up the hosting providers behind our customer IPs as seen in our request logs (to find out what people think is a good idea for hosting a production web- or mobile-app service backend these days.) By and large, our very-much "real world" customers are "self hosting" — usually on bare metal rather than a VPS, and usually with providers you've probably never heard of (ColoCrossing and ServerMania seem to come up fairly often among our US-based customers.) These hosting providers are all very much in the style of "you lease each machine as a separate contract; each machine gets one public IPv4 address included in the cost; private networking [i.e. an explicit VLAN] is an extra optional feature you can enable after the fact, and only works between higher-end machine types, rather than being a given, because our lower-end machines only have a single NIC in them [besides the one that's part of the BMC used for IPMI]." What I assume is happening here isn't literal "self hosting" — these random non-IT-oriented customers wouldn't know the first thing about it — but rather that a given customer of ours has paid some "vertically-integrated IT consultancy" to both build and host their service for them; and said consultancy has chosen to use bare-metal hosting to host the resulting service, to minimize their own OpEx, and therefore maximize their margins. (In fact, I bet they're often packing several such customers onto a single box.) --- Also, in a more professional capacity, I investigate the hosts behind IP addresses behind bulk-registration / DDoS attacks against our platform, in order to create signatures for them. Given the way some of these attacks seem to work, a large number of machines on the Internet — especially in Russia and [some parts of] Africa — seemingly aren't only un-NATed, but in fact have a public /24 or even /22 directly attached to a single box! (If traffic was originating from a random subset of a /24, it could just be someone spinning up a hundred VMs on top of some small colo's OpenStack deployment, sure. But tandem traffic from every IP in a /24, and only exactly said /24? That looks pretty much exactly like the sort of tandem IPv6 traffic that is generated when a box has a /48 or /56 assigned to it.)
adev_ 4y ago
> The claim is that IPv4 + NAT + bad firewall is better than IPv6 + bad firewall. Even that is not true: - It takes half-minute to scan an IPv4 public IP (NAT) for vulnerabilities. - Good luck and have fun to scan a /64 for a potentially vulnerable machine. See you next century. - And if it is not enough: most internet box support UPnP/NAT-PMP that allow any malware to get your NAT wild opened.

derefr 4y ago

What makes you think that, for critical systems, "IPv4 + NAT + bad firewall" is the default IPv4 deployment paradigm, rather than "IPV4 + bad firewall"? Sure, big IaaS providers like AWS put you in a VPC by default. But most servers on the net are not hosted in an IaaS; they're hosted using a VPS or bare-metal hosting provider, or just coloed in a DC by their owner. And in all those cases, what that kind of deployment gets you, is a public IPv4 per VM/machine, that anyone on the Internet can march right up and talk to, where it's the responsibility of the machine itself to reject incoming packets (i.e. at the OS level with a kernel firewall.) NAT on IPv4 is only really a default assumption for residential networks. Anywhere else, it's pretty much like the movie WarGames: even the mainframe has a phone number you can call. Staying on IPv4 isn't making anyone safe.

293984j29384 4y ago
While I don't have any factual proof to refute your statements, in my personal experience almost every organization uses NAT & RFC1918 address space. The only client I can think of in my 20 years of experience that used a public IPv4 per VM/machine was the DoD, specifically, the U.S. Army. From your very last statement, I think you've confused self hosting (like buying a VPS from Digital Ocean and hosting your own blag) and how the real world works (like going to Dell.com and ordering a new laptop). "The mainframe" these days is almost always behind a L4/L7 load balancer or other network device and very rarely directly addressable.
- SoftTalker 4y ago
  Big universities (at least in my experience in the USA) are the other ones that would have a public IP address for every device, at least until rather recently. They were online very early and got allocated huge blocks of addresses, before anyone really imagined future scarcity.
  - icedchai 4y ago
    In the mid-90's, every system at my university had a public IP address, including those on the campus residential networks. There were no firewalls. It was also a flat address space (/16, 255.255.0.0) for the whole campus! The 90's were certainly a different time.
- derefr 4y ago
  My company runs an API SaaS; my impressions come from a hobby I have of looking up the hosting providers behind our customer IPs as seen in our request logs (to find out what people think is a good idea for hosting a production web- or mobile-app service backend these days.) By and large, our very-much "real world" customers are "self hosting" — usually on bare metal rather than a VPS, and usually with providers you've probably never heard of (ColoCrossing and ServerMania seem to come up fairly often among our US-based customers.) These hosting providers are all very much in the style of "you lease each machine as a separate contract; each machine gets one public IPv4 address included in the cost; private networking [i.e. an explicit VLAN] is an extra optional feature you can enable after the fact, and only works between higher-end machine types, rather than being a given, because our lower-end machines only have a single NIC in them [besides the one that's part of the BMC used for IPMI]." What I assume is happening here isn't literal "self hosting" — these random non-IT-oriented customers wouldn't know the first thing about it — but rather that a given customer of ours has paid some "vertically-integrated IT consultancy" to both build and host their service for them; and said consultancy has chosen to use bare-metal hosting to host the resulting service, to minimize their own OpEx, and therefore maximize their margins. (In fact, I bet they're often packing several such customers onto a single box.) --- Also, in a more professional capacity, I investigate the hosts behind IP addresses behind bulk-registration / DDoS attacks against our platform, in order to create signatures for them. Given the way some of these attacks seem to work, a large number of machines on the Internet — especially in Russia and [some parts of] Africa — seemingly aren't only un-NATed, but in fact have a public /24 or even /22 directly attached to a single box! (If traffic was originating from a random subset of a /24, it could just be someone spinning up a hundred VMs on top of some small colo's OpenStack deployment, sure. But tandem traffic from every IP in a /24, and only exactly said /24? That looks pretty much exactly like the sort of tandem IPv6 traffic that is generated when a box has a /48 or /56 assigned to it.)

adev_ 4y ago

> The claim is that IPv4 + NAT + bad firewall is better than IPv6 + bad firewall. Even that is not true: - It takes half-minute to scan an IPv4 public IP (NAT) for vulnerabilities. - Good luck and have fun to scan a /64 for a potentially vulnerable machine. See you next century. - And if it is not enough: most internet box support UPnP/NAT-PMP that allow any malware to get your NAT wild opened.