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There’s anonymity on the Internet. Get over it.

October 27, 2009 by

In a recent interview prominent antivirus developer Eugene Kaspersky decried the role of anonymity in cybercrime. This is not a new claim – it is touched on in the Commission on Cybersecurity for the 44th Presidency Report and Cybersecurity Act of 2009, among others – but it misses the mark. Any Internet design would allow anonymity. What renders our Internet vulnerable is primarily weakness of software security and authentication, not anonymity.

Consider a hypothetical of three Internet users: Alice, Bob, and Charlie. If Alice wants to communicate anonymously with Charlie, she may relay her messages through Bob. While Charlie knows Bob is an intermediary, Charlie does not know with whom he is ultimately communicating. For even greater anonymity Alice can pass her messages through multiple Bobs, and by applying cryptography she can ensure no individual Bob can piece together that she is communicating with Charlie. This basic approach to anonymity is remarkable in its independence of the Internet’s design: it only requires that some Bob(s) can and do run intermediary software. Even on an Internet where users could verify each other’s identity this means of anonymity would remain viable.

The sad state of software security – the latest DHS weekly bulletin alone identified over 40 “high severity” vulnerabilities – is what enables malicious users to exploit the Internet’s indelible capacity for anonymity. Modifying the prior hypothetical, suppose Alice now wants to spam, phish, denial of service (DoS) attack, or hack Charlie. After compromising Bob’s computer with malicious software (malware), Alice can send emails, host websites, and launch DoS attacks from it; Charlie knows Bob is apparently misbehaving, but has no means of discovering Alice’s role. Nearly all spam, phishing, and DoS attacks are now perpetrated with networks of compromised computers like Bob’s (botnets). At the writing of a July 2009 private sector report, just five botnets sourced nearly 75% of spam. Worse yet, botnets are increasingly self-perpetuating: spam and phishing websites propagate malware that compromises new computers for the botnet.

Shortcomings in authentication, the means of proving one’s identity either when necessary or at all times, are a secondary contributor to the Internet’s ills. Most applications rely on passwords, which are easily guessed or divulged through deception – the very mechanisms of most phishing and account hijacking. There are potential technical solutions that would enable a user to authenticate themselves without the risk of compromising accounts. But any approach will be undermined by weaknesses in underlying software security when a malicious party can trivially compromise a user’s computer.

The policy community is already trending towards acceptance of Internet anonymity and refocusing on software security and authentication; the recent White House Cyberspace Policy Review in particular emphasizes both issues. To the remaining unpersuaded, I can only offer at last a truism: There’s anonymity on the Internet. Get over it.

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Net Neutrality: When is Network Management "Reasonable"?

October 26, 2009 by

Last week the FCC released its much-awaited Notice of Proposed Rulemaking (NPRM) on network neutrality. As expected, the NPRM affirms past FCC neutrality principles, and adds two more. Here’s the key language:

1. Subject to reasonable network management, a provider of broadband Internet access service may not prevent any of its users from sending or receiving the lawful content of the user’s choice over the Internet.

2. Subject to reasonable network management, a provider of broadband Internet access service may not prevent any of its users from running the lawful applications or using the lawful services of the user’s choice.

3. Subject to reasonable network management, a provider of broadband Internet access service may not prevent any of its users from connecting to and using on its network the user’s choice of lawful devices that do not harm the network.

4. Subject to reasonable network management, a provider of broadband Internet access service may not deprive any of its users of the user’s entitlement to competition among network providers, application providers, service providers, and content providers.

5. Subject to reasonable network management, a provider of broadband Internet access service must treat lawful content, applications, and services in a nondiscriminatory manner.

6. Subject to reasonable network management, a provider of broadband Internet access service must disclose such information concerning network management and other practices as is reasonably required for users and content, application, and service providers to enjoy the protections specified in this part.

That’s a lot of policy packed into (relatively) few words. I expect that my colleagues and I will have a lot to say about these seemingly simple rules over the coming weeks.

Today I want to focus on the all-purpose exception for “reasonable network management”. Unpacking this term might tell us a lot about how the proposed rule would operate.

Here’s what the NPRM says:

Reasonable network management consists of: (a) reasonable practices employed by a provider of broadband Internet access to (i) reduce or mitigate the effects of congestion on its network or to address quality-of-service concerns; (ii) address traffic that is unwanted by users or harmful; (iii) prevent the transfer of unlawful content; or (iv) prevent the unlawful transfer of content; and (b) other reasonable network management practices.

The key word is “reasonable”, and in that respect the definition is nearly circular: in order to be “reasonable”, a network management practice must be (a) “reasonable” and directed toward certain specific ends, or (b) “reasonable”.

In the FCC’s defense, it does seek comments and suggestions on what the definition should be, and it does say that it intends to make case-by-case determinations in practice, as it did in the Comcast matter. Further, it rejects a “strict scrutiny” standard of the sort that David Robinson rightly criticized in a previous post.

“Reasonable” is hard to define because in real life every “network management” measure will have tradeoffs. For example, a measure intended to block copyright-infringing material would in practice make errors in both directions: it would block X% (less than 100%) of infringing material, while as a side-effect also blocking Y% (more than 0%) of non-infringing material. For what values of X and Y is such a measure “reasonable”? We don’t know.

Of course, declaring a vague standard rather than a bright-line rule can sometimes be good policy, especially where the facts on the ground are changing rapidly and it’s hard to predict what kind of details might turn out to be important in a dispute. Still, by choosing a case-by-case approach, the FCC is leaving us mostly in the dark about where it will draw the line between “reasonable” and “unreasonable”.

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Intractability of Financial Derivatives

October 15, 2009 by

A new result by Princeton computer scientists and economists shows a striking application of computer science theory to the field of financial derivative design. The paper is Computational Complexity and Information Asymmetry in Financial Products by Sanjeev Arora, Boaz Barak, Markus Brunnermeier, and Rong Ge. Although computation has long been used in the financial industry for program trading and “the thermodynamics of money”, this new paper applies an entirely different kind of computer science: Intractability Theory.

A financial derivative is a contract specifying a payoff calculated by some formula based on the yields or prices of a specific collection of underlying assets. Consider the securitization of debt: a CDO (collateralized debt obligation) is a security formed by packaging together hundreds of home mortgages. The CDO is supposedly safer than the individual mortgages, since it spreads the risk (not every mortgage is supposed to default at once). Furthermore, a CDO is usually divided into “senior tranches” which are guaranteed not to drop in value as long as the total defaults in the pool does not exceed some threshhold; and “junior tranches” that are supposed to bear all the risk.

Trading in derivatives brought down Lehman Brothers, AIG, and many other buyers, based on mistaken assumptions about the independence of the underlying asset prices; they underestimated the danger that many mortgages would all default at the same time. But the new paper shows that in addition to that kind of danger, risks can arise because a seller can deliberately construct a derivative with a booby trap hiding in plain sight.

It’s like encryption: it’s easy to construct an encrypted message (your browser does this all the time), but it’s hard to decrypt without knowing the key (we believe even the NSA doesn’t have the computational power to do it). Similarly, the new result shows that the seller can construct the CDO with a booby trap, but even Goldman Sachs won’t have enough computational power to analyze whether a trap is present.

The paper shows the example of a high-volume seller who builds 1000 CDOs from 1000 asset-classes of home mortages. Suppose the seller knows that a few of those asset classes are “lemons” that won’t pay off. The seller is supposed to randomly distribute the asset classes into the CDOs; this minimizes the risk for the buyer, because there’s only a small chance that any one CDO has more than a few lemons. But the seller can “tamper” with the CDOs by putting most of the lemons in just a few of the CDOs. This has an enormous effect on the senior tranches of those tampered CDOs.

In principle, an alert buyer can detect tampering even if he doesn’t know which asset classes are the lemons: he simply examines all 1000 CDOs and looks for a suspicious overrepresentation of some of the asset classes in some of the CDOs. What Arora et al. show is that is an NP-complete problem (“densest subgraph”). This problem is believed to be computationally intractable; thus, even the most alert buyer can’t have enough computational power to do the analysis.

Arora et al. show it’s even worse than that: even after the buyer has lost a lot of money (because enough mortgages defaulted to devalue his “senior tranche”), he can’t prove that that tampering occurred: he can’t prove that the distribution of lemons wasn’t random. This makes it hard to get recourse in court; it also makes it hard to regulate CDOs.

Intractability Theory forms the basis for several of the technologies discussed on Freedom-to-Tinker: cryptography, digital-rights management, watermarking, and others. Perhaps now financial policy is now another one.

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Sidekick Users' Data Lost: Blame the Cloud?

October 14, 2009 by

Users of Sidekick mobile phones saw much of their data disappear last week due to engineering problems at a Microsoft data center. Sidekick devices lose the contents of their memory when they don’t have power (e.g. when the battery is being changed), so all data is transmitted to a data center for permanent storage — which turned out not to be so permanent.

(The latest news is that some of the data, perhaps most of it, may turn out to be recoverable.)

A common response to this story is that this kind of danger is inherent in “cloud” computing services, where you rely on some service provider to take care of your data. But this misses the point, I think. Preserving data is difficult, and individual users tend to do a mediocre job of it. Admit it: You have lost your own data at some point. I know I have lost some of mine. A big, professionally run data center is much less likely to lose your data than you are.

It’s worth noting, too, that many cloud services face lower risk of this sort of problem. My email, for example, lives in the cloud–the “official copy” is on a central server, and copies are downloaded frequently to my desktop and laptop computers. If the server were to go up in flames, along with all of the server backups, I would still be in good shape, because I would still have copies of everything on my desktop and laptop.

For my email and similar services, the biggest risk to data integrity is not that the server will disappear altogether, but that the server will misbehave in subtle ways, causing my stored data to be corrupted over time. Thanks to the automatic synchronization between the server and my two clients (desktop and laptop), bad data could be replicated silently into all copies. In principle, some of the damage could be repaired later, using the server’s backups, but that’s a best case scenario.

This risk, of buggy software corrupting data, has always been with us. The question is not whether problems will happen in the cloud — in any complex technology, trouble comes with the territory — but whether the cloud makes a problem worse.

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PrivAds: Behavioral Advertising without Tracking

October 12, 2009 by

There’s an interesting new paper out of Stanford and NYU, about a system called “PrivAds” that tries to provide behavioral advertising on web sites, without having a central server gather detailed information about user behavior. If the paper’s approach turns out to work, it could have an important impact on the debate about online advertising and privacy.

Advertisers have obvious reasons to show you ads that match your interests. You can benefit too, if you see ads that are relevant to your needs, rather than ones you don’t care about. The problem, as I argued in my Congressional testimony, comes when sites track your activities, and build up detailed files on you, in order to do the targeting.

PrivAds tries to solve this problem by providing behavioral advertising without having any server track you. The idea is that your own browser will track you, and analyze your online activities to build a model of your interests, but your browser won’t reveal this information to anyone else. When a site wants to show you an interest-based ad, your browser will choose the ad from a portfolio of ads offered by the ad service.

The tricky part is how your browser can do all of this without incidentally leaking your activities to the server. For example, the ad agency needs to know how many times each ad was shown. How can you report this to the ad service without revealing which ads you saw? PrivAds offers a solution based on fancy cryptography, so that the ad agency can aggregate reports from many users, without being able to see the users’ individual reports. Similarly, every interaction between your browser and the outside must be engineered carefully so that behavioral advertising can occur but the browser doesn’t telegraph your actions.

It’s not clear at this point whether the PrivAds approach will work, in the sense of protecting privacy without reducing the effectiveness of ad targeting. It’s clear, though, that PrivAds is asking an important question.

If the PrivAds approach succeeds, demonstrating that behavioral advertising does not require tracking, this doesn’t mean that companies will stop wanting to track you — but it does mean that they won’t be able to use advertising as an excuse to track you.

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