July 15, 2024

Archives for October 2007

Eavesdropping as a Telecom Profit Center

In 1980 AT&T was a powerful institution with a lucrative monopoly on transporting long-distance voice communications, but forbidden by law from permitting the government to eavesdrop without a warrant. Then in 1981 Judge Greene took its voice monopoly away, and in the 1980s and 90s the Internet ate the rest of its lunch. By 1996, Nicholas Negroponte wrote what many others also foresaw: “Shipping bits will be a crummy business. Transporting voice will be even worse. By 2020 … competition will render bandwidth a commodity of the worst kind, with no margins and no real basis for charging anything.

During the 1980s and 90s, AT&T cleverly got out of any business except shipping commodity bits: in 1981 it (was forced to) split off its regional phone companies; in 1996 it (voluntarily) split off its equipment-making arm as Lucent Technologies; in 2000-2001 it sold off its Wireless division to raise cash. Now AT&T long-distance bit-shipping is just a division of the former SBC, renamed AT&T.

What profit centers are left in shipping commodity bits? The United States Government spends 44 billion dollars a year on its spy agencies. It’s very plausible that the NSA is willing to pay $100 million or more for a phone/internet company to install a secret room where the NSA can spy on all the communications that pass through. A lawsuit by the EFF alleges such a room, and its existence was implicitly confirmed by the Director of National Intelligence in an interview with the El Paso Times. We know the NSA spends at least $200 million a year on information-technology outsourcing and some of this goes to phone companies such as Verizon.

Therefore, if it’s true that AT&T has such a secret room, then it may be simply that this is the only way AT&T knows how to make money off of shipping bits: it sells to the government all the information that passes through. Furthermore, economics tells us that in a commodity market, if one vendor is able to lower its price below cost, then other vendors must follow unless they also are able to make up the difference somehow. That is, there will be substantial economic pressure on all the other telecoms to accept the government’s money in exchange for access to everybody’s mail, Google searches, and phone calls.

In the end, it could be that the phone companies that cooperated with the NSA did so not for reasons of patriotism, or because their arms were twisted, but because the NSA came with a checkbook. Taking the NSA’s money may be the only remaining profit center in bit-shipping.

AT&T Explains Guilt by Association

According to government documents studied by The New York Times, the FBI asked several phone companies to analyze phone-call patterns of Americans using a technology called “communities of interest”. Verizon refused, saying that it didn’t have any such technology. AT&T, famously, did not refuse.

What is the “communities of interest” technology? It’s spelled out very clearly in a 2001 research paper from AT&T itself, entitled “Communities of Interest” (by C. Cortes, D. Pregibon, and C. Volinsky). They use high-tech data-mining algorithms to scan through the huge daily logs of every call made on the AT&T network; then they use sophisticated algorithms to analyze the connections between phone numbers: who is talking to whom? The paper literally uses the term “Guilt by Association” to describe what they’re looking for: what phone numbers are in contact with other numbers that are in contact with the bad guys?

When this research was done, back in the last century, the bad guys where people who wanted to rip off AT&T by making fraudulent credit-card calls. (Remember, back in the last century, intercontinental long-distance voice communication actually cost money!) But it’s easy to see how the FBI could use this to chase down anyone who talked to anyone who talked to a terrorist. Or even to a “terrorist.”

Here are a couple of representative diagrams from the paper:

Fig. 4. Guilt by association – what is the shortest path to a fraudulent node?

Fig. 5. A guilt by association plot. Circular nodes correspond to wireless service accounts while rectangular nodes are conventional land line accounts. Shaded nodes have been previously labeled as fraudulent by network security associates.

Comcast and Net Neutrality

The revelation that Comcast is degrading BitTorrent traffic has spawned many blog posts on how the Comcast incident bolsters the blogger’s position on net neutrality – whatever that position happens to be. Here is my contribution to the genre. Mine is different from all the others because … um … well … because my position on net neutrality is correct, that’s why.

Let’s start by looking at Comcast’s incentives. Besides being an ISP, Comcast is in the cable TV business. BitTorrent is an efficient way to deliver video content to large numbers of consumers – which makes BitTorrent a natural competitor to cable TV. BitTorrent isn’t a major rival yet, but it might plausibly develop into one. Which means that Comcast has an incentive to degrade BitTorrent’s performance and reliability, even when BitTorrent isn’t in any way straining Comcast’s network.

So why is Comcast degrading BitTorrent? Comcast won’t say. They won’t even admit what they’re doing, let alone offer a rationale for it, so we’re left to speculate. The technical details of Comcast’s blocking are only partially understood, but what we do know seems hard to square with claims that Comcast is using the most effective means to optimize some resource in their network.

Now pretend that you’re the net neutrality czar, with authority to punish ISPs for harmful interference with neutrality, and you have to decide whether to punish Comcast. You’re suspicious of Comcast, because you can see their incentive to bolster their cable-TV monopoly power, and because their actions don’t look like a good match for the legitimate network management goals that they claim motivate their behavior. But networks are complicated, and there are many things you don’t know about what’s happening inside Comcast’s network, so you can’t be sure they’re just trying to undermine BitTorrent. And of course it’s possible that they have mixed motives, needing to manage their network but choosing a method that had the extra bonus feature of hurting BitTorrent. You can ask them to justify their actions, but you can expect to get a lawyerly, self-serving answer, and to expend great effort separating truth from spin in that answer.

Are you confident that you, as net neutrality czar, would make the right decision? Are you confident that your successor as net neutrality czar, who would be chosen by the usual political process, would also make the right decision?

Even without a regulatory czar, wheels are turning to punish Comcast for what they’ve done. Customers are unhappy and are putting pressure on Comcast. If they deceived their customers, they’ll face lawsuits. We don’t know yet how things will come out, but it seems likely Comcast will regret their actions, and especially their lack of transparency.

All of which – surprise surprise – confirms my position on net neutrality: there is a risk of harmful behavior by ISPs, but writing and enforcing neutrality regulation is harder than it looks, and non-regulatory forces may constrain ISPs enough.

Comcast Blocks Some Traffic, Won't Explain Itself

Comcast’s apparent policy of blocking some BitTorrent traffic, which has been discussed on tech sites [example] for months, has now broken out into the mainstream press. Comcast is making things worse by refusing to talk plainly about what they are doing and why. (This is an improvement over Comcast’s previously reported denials, which now appear to be inconsistent with the facts.)

To the extent that Comcast has explained itself, its story seems to be that it is slowing traffic from heavy users in order to keep the network moving smoothly. This would be a reasonable thing for Comcast to do (if they were open about it) – but it’s not quite what they’re actually doing.

For starters, Comcast’s measures are not aimed at heavy users but rather at users of certain protocols such as BitTorrent. And not even all users of BitTorrent are targeted, but only those who use BitTorrent in a particular way: uploading a file to non-Comcast users while not simultaneously downloading parts of the same file. (In BitTorrent jargon, this is called “seeding”.) To get an idea of how odd this is, consider that an uploader who is experiencing blocking can apparently avoid the blocking by adding some download traffic.

It would likely be easier for Comcast to simply measure how much traffic each user is generating and drop the heaviest users’ packets, or just to discard packets at random (a tactic that falls most heavily on those who send and receive the most packets).

Beyond its choice of what to block, Comcast is using an unusual and nonstandard form of blocking.

There are well-established mechanisms for dealing with traffic congestion on the Internet. Networks are supposed to respond to congestion by dropping packets; endpoint computers notice that their packets are being dropped and respond by slowing their transmissions, thus relieving the congestion. The idea sounds simple, but getting the details right, so that the endpoints slow down just enough but not too much, and the network responds quickly to changes in traffic level but doesn’t overreact, required some very clever, subtle engineering.

What Comcast is doing instead is to cut off connections by sending forged TCP Reset packets to the endpoints. Reset packets are supposed to be used by one endpoint to tell the other endpoint that an unexplained, unrecoverable error has occurred and therefore communication cannot continue. Comcast’s equipment (apparently made by a company called Sandvine) seems to send both endpoints a Reset packet, purporting to come from the other endpoint, which causes both endpoints to break the connection. Doing this is a violation of the TCP protocol, which has at least two ill effects: it bypasses TCP’s well-engineered mechanisms for handling congestion, and it erodes the usefulness of Reset packets as true indicators of error.

People have apparently figured out already how to defeat this blocking, and presumably it won’t be long before BitTorrent clients incorporate anti-blocking measures.

It looks like Comcast is paying the price for trying to outsmart their customers.

The ease of applying for a home loan

I’m currently in the process of purchasing a new house. I called up a well-known national bank and said I wanted a mortgage. In the space of 30 minutes, I was pre-approved, had my rates locked in, and so forth. Pretty much the only identifying information I had to provide was the employer, salary, and social security number for myself and my wife, as well as some basic stats on our investment portfolio. Interestingly, the agent said that for people in my situation (sterling credit, paying more than 20% of the down payment out of our own pocket), they believe I’m highly unlikely to ever default on the loan. As a result, they do not need me to go the trouble of documenting my income or assets beyond what I told them over the phone. They’ll take my word for it.

(In an earlier post, I discussed my name and social security number having been stolen from where they had been kept in Ohio. Ohio gave me a free subscription to Debix, which claims to be able to intercept requests to read my credit report, calling my cell phone to ask for my permission. Why not? I signed up. Well, my cell phone never buzzed with any sort of call from Debix. Their service, whatever it does, had no effect here.)

Obviously, there’s a lot more to finalizing a loan and completing the purchase of a home than there is to getting approved for a loan and locking a rate. Nonetheless, it’s striking how little personal information I had to divulge to get this far into the game. Could somebody who knew my social security number use this mechanism to borrow money against my good credit and run away to a Carribean island with the proceeds? I would have to hope that there’s some kind of mechanism further down the pipeline to catch such fraud, but it’s not too hard to imagine ways to game this system, given what I’ve observed so far.

Needless to say, once this home purchase is complete, I’ll be freezing my credit report. Let’s just hope the freezing mechanism is more useful than Debix’s notification system.

(Sidebar: an $18 charge appeared on my credit card last month for a car rental agency that I’ve never used, claiming to have a “swipe” of my credit card. I challenged it, so now the anti-fraud division is allegedly attempting to recover the signed charge slip from the car rental agency. The mortgage agent, mentioned above, saw a note in my credit report on this and asked me if I had “challenged my bank”. I explained the circumstances and all was well. However, it’s interesting to note that the “challenge”, as it apparently appears in my credit report, doesn’t have any indication as to what’s being challenged or how significant it might be. Again, the agent basically took my word for it.)