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Remotely Counting Machines Behind A NAT Box
Overtone writes "Steve Bellovin of AT&T Labs Research has published a paper showing how to remotely count the number of machines hiding behind a NAT box (in IMW 2002, the
Second Internet Measurement Workshop). Your friendly DSL or cable broadband provider could implement this technique to enforce their single-machine license clause. Bellovin explains how to change the NAT software to defeat the measurement scheme, but the fix is complicated and unlikely to appear in commercial home gateways anytime soon."
It's already here: SpeakEasy.
Their TOS explicitly states:
"Speakeasy believes in the right of the individual to publish information they feel is important to the world via the Internet. Unlike many ISP's, Speakeasy allows customers to run servers (web, mail, etc.) over their Internet connections, use hubs, and share networks in multiple locations."
There are already several simpler ways:
1. Use proxies instead of NAT and proxy transparently if needed. Yeah, I know, none of the P2P download sucker shit as it does not have proxies but such is life.
2. Use OSes with better randomisation of IP IDs. This is a tuneable parameter on most OSes and after you have turned it on the graphs are no longer so pretty.
Baker's Law: Misery no longer loves company. Nowadays it insists on it
http://www.sigsegv.cx/
One of the grsecurity patches for the kernel already gives Linux the random IPid field.
Wouldn't make a jot of difference. The current firewalls aren't rewriting the IPid field anyway, so adding an extra hop would not affect the analysis at all.
In reading the paper, it is apparent that this is not a particularly cheap thing to attempt. I can't see how it could be easily automated and deployed on a large scale, even assuming someone could be sufficiently bothered to do so.
If you want protection from this, you're going to need to do some serious work on iptables to add tracking of fragments to the connection tracking code and to rewrite the field on outbound packets to some psuedo-random value. Interestingly this is the "correct" thing to do anyway - otherwise it is theoretically possible to generate two packets with the same id, both fragmented from different internal hosts to the same destination, and screw up the fragmentation reassembly at the receiver.
Tim
With franchise agreements to the cable companies, not necessarily true.
I don't see anything but a poor rationalization in your arguement suggesting that it's not *YOUR* fault that you NEED to break your contract
What about the chance that the contract may be illegal? There's the nice little FCC regulation that the cable company/phone company can't say squat about what happens inside your house provided you don't get services you don't pay for (You're paying for one IP, not one computer in reality) and you don't degrade the service of others.
"you're going to need to do some serious work on iptables "
Another user already posted that there's already a patch (or kernel option) for linux to do random ipid's just like BSD does.
This is more an admin utility than a policing tool. Just kick back, get yourself a beer and watch the knee-jerk reactions and paranoid theories from all the nerds who think the man is out the get 'em.
I don't need no instructions to know how to rock!!!!
History does not bode well for the broadband providers on this. If one recalls back in the day, the Telco (MA-Bell/AT&T) user to tack on an additional charge for every actual receiver (that you were forced to rent from them) on the phone line. For those who know POTS (plain old telephone system) an extension can be added but just tapping a wire onto the existing wire in the house. However when MA-bell got broken up in the 70s(?) I believe they did away with this foofah, and you paid for the telephone *service*
CATV (cable) used to be the same way.. you day to pay extra for each TV. And then they stopped doing that and you paid for *service* of the signal.
Now here is where it gets tricky, unlike POTS and analog CATV the line is hot or its not (so to speak), broadband you actually have discrete data you are passing around. This should be the *service*. However it could end up being a pay as you go service (bad for the users, good for the money grubbers) or a limited throughput 'unlimited' service (which is mostly how it is now). Currently I don?t see a metered usage model flying right now and this is why:
Everyone that adopted broadband early wanted it (and could get it) go it. Dialup services are cheap and unlimited. If you start charging for broadband based on usage you aren?t not very attractive to those people you want to take away from dialup who are complacent and will cope with what they have. A metered service is not (in consumers minds) a *NOT* better value than an unmetered service.
As we know there is a mega glut of fiber, broadband should be getting cheaper rather than more expensive.. but that?s another article. Its going to be hard to justify metering people when there is so much capacity unused. (hopefully supply and demand will work out here).
Now this is what is going to happen, when a critical mass of people stop using dialup, and then modems stop coming standard in computers, and then the broadband guys think they have a captive audience they will get everyone in the cartel on board and raise rates and meter usage. What?s worse is that they will claim there is a lack of long haul bandwidth, which probably wont be true, because as the broadband market picks up they will still be doing expansion of the network because of the expectation of even larger amounts of growth.
Conclusion, this are probably good for the short term, *VERY* bad for the long term.
PS the document was spell checked for those with delicate constitutions.
"I dont agree. It's not your local ISPs fault that there aren't multiple providers in your area (assuming we are talking about you) or multiple service options. If there was enough money to be made in an area, there would most likely be more providers."
I'm not sure what world you're living in. It IS MOST ASSUREDLY my local ISP's fault that there are not multiple provider's in my area.
Verizon ran every dirty trick in the book to stop me from getting access through DSLi (out of Florida, who had an EXCELLENT TOS) instead of buying Verizon's restricted, overpriced DSL in North Carolina. I fought with them for over 14 months. I called the friggin' Utilities Commission on them. Unfortunately, by the time that bore fruit, every intelligently run provider had read the writing on the wall -- there's no way to make a profit when every single customer has to fight through the SUC for over a year, for God's sake.
The reason I am stuck with crappy TOS is because of Verizon, straight and simple. Verizon covers something like 20% of the country. Most of the Baby Bells aren't any better.
I'm not saying everyone who has a NAT fought with a Baby Bell for a year. But most of them have been cheated out of a decent, affordable TOS by one.
Since virtually none exist because of illegal behavior, you shouldn't be so surprised or indignant that many folks choose to get around them.
Who is RTFM and when will he help me with Unix?
The field they are using is the IP id field, which exists in all IP packets (including UDP, ICMP, whatever), and which is used for low-level packet reassembly. On many OS'es, this is a globally increasing counter, i.e. two distinct connections on the same machine share the same counter, but two connections on different machines do not.
Workarounds:
Say no to software patents.
Just for your information: Many of those p2p applications support SOCKS 4 + 5 proxies. (Morpheus/Kazaa, WinMX, AG did..)
here's one.
Seems a little arbitrary, but they're small fry. let's go bigger:
here's another.
I think this bit applies to the question at hand (emphasis is mine):
How does this imply that you can't share a DSL connection? OTOH, it explicitly says that sharing a connection is OK.
however, if we look to AT&T DSL TOS, they are somewhat more restrictive:
A little tougher, but it doesn't actually rule out connection-sharing entirely- just requires that AT&T grant you permission, right? So they must have a process for granting the approval, and a list of approved equipment.
Since I'm bored today, I called them up. I pointed the nice lady at their TOS, section 8(a), and asked if she could provide me with a list of AT&T approved equipment, and/or the approval process for home networking. She put me on hold for a bit. When she came back, she told me that AT&T DSL is not the same as AT&T WORLDnet DSL, and i had the wrong phone number- but WORLDnet doesn't allow any kind of connection sharing- and she'd happily transfer me to the REAL AT&T. The second phone monkey had no idea what I was talking about- ditto the 3rd. Neither of them could understand why I would want to ask questions about their TOS if they couldn't even deliver service to my residence. The fourth phone monkey told me that they don't support any kind of multiple connection, and that the "grant you permission" line is in the contract for things like automated security systems that call the police department when someone breaks into your house.
So. Score: SBC +1 (but -1 for their stupid 'frames' patent), AT&T 0. Interesting article, but since I'm on SBC, i won't be changing my NAT settings...
Humpty Dumpty was pushed.
Fragments having the same ipid field are assembled. Indedd, Ipid only changes from one packet to the next, but not from one fragment to the next.
Say no to software patents.
Hmmmm this little module lets onw configure how you want the IP header id generatored, among a bunch of other options to hide identify. Why not just work this into iptables, PF, IPF and no worries about NAT ID'ing.