November 23, 2024

Does the Great Firewall Violate U.S. Law?

Clayton, Murdoch, and Watson have an interesting new paper describing technical mechanisms that the Great Firewall of China uses to block online access to content the Chinese government doesn’t like.

The Great Firewall works in two parts. One part inspects data packets that cross the border between China and the rest of the world, looking for “bad” content. The other part tries to shut down cross-border connections that have contained “bad” content. I’ll focus here on the shutdown part.

The shutdown part attacks the TCP protocol, which is used (among many other things) to transfer Web pages and email. TCP allows two computers on the Net to establish a virtual “connection” and then send data over that connection. The technical specification for TCP says that either of the two computers can send a so-called Reset packet, which informs the computer on the other end that some unspecified error has occurred so the connection should be shut down immediately.

The Great Firewall tries to sever TCP connections by forging Reset packets. Each endpoint machine is sent a series of Reset packets purporting to come from the other machine (but really coming from the Great Firewall). The endpoints usually respond by shutting down the connection. If they try to connect again, they’ll get more forged Reset packets, and so on.

This trick of forging Reset packets has been used by denial-of-service attackers in the past, and there are well-known defenses against it that have been built into popular networking software. However, these defenses generally don’t work against an attacker who can see legitimate traffic between the target machines, as the Great Firewall can.

What the Great Firewall is doing, really, is launching a targeted denial of service attack on both ends of the connection. If I visit a Chinese website and access certain content, the Great Firewall will send denial of service packets to a machine in China, which probably doesn’t violate Chinese law. But it will also send denial of service packets to my machine, here in the United States. Which would seem to implicate U.S. law.

The relevant U.S. statute is the Computer Fraud and Abuse Act (18 U.S.C. 1030), which makes it an offense to “knowingly cause[] the transmission of a program, information, code, or command, and as a result of such conduct, intentionally cause[] damage without authorization, to a protected computer”, as long as certain other conditions are met (about which more below). Unpacking this, and noting that any computer that can communicate with China will meet the definition of “protected computer”, the only part of this requirement that requires any discussion is “damage”. The statute defines “damage” as “any impairment to the integrity or availability of data, a program, a system, or information”, so that the unavailability to me of the information on the Chinese website I tried to visit would count as damage.

But the offense has another requirement, which is intended to ensure that it is serious enough to merit legal attention. The offense must also cause, or attempt to cause, one of the following types of harm:

(i) loss to 1 or more persons during any 1-year period (and, for purposes of an investigation, prosecution, or other proceeding brought by the United States only, loss resulting from a related course of conduct affecting 1 or more other protected computers) aggregating at least $5,000 in value;

(ii) the modification or impairment, or potential modification or impairment, of the medical examination, diagnosis, treatment, or care of 1 or more individuals;

(iii) physical injury to any person;

(iv) a threat to public health or safety; or

(v) damage affecting a computer system used by or for a government entity in furtherance of the administration of justice, national defense, or national security;

This probably wouldn’t apply to an attack on my computer, but attacks on certain U.S. government entities would trigger part (v), and there is a decent argument that the aggregate effect of such attacks on U.S. persons could add up to more than $5000 in damage, which would trigger part (i). I don’t know whether this argument would succeed. And I’m not a lawyer, so I’m relying on real lawyers to correct me in the comments if I’m missing something here.

But even if the Great Firewall doesn’t violate U.S. law now, the law could be changed so that it did. A law banning the sending of forged packets to the U.S. with intent to deny availability of content lawful in the U.S., would put the Great Firewall on the wrong side of U.S. law. And it would do so without reaching across the border to regulate how the Chinese government interacts with its citizens. If we can’t stop the Chinese government from censoring their own citizens’ access to the Net, maybe we can stop them from launching denial of service attacks against us.

(link via Bruce Schneier)

Art of Science, and Princeton Privacy Panel

Today I want to recommend two great things happening at Princeton, one of which is also on the Net.

Princeton’s second annual Art of Science exhibit was unveiled recently, and it’s terrific, just like last year. Here’s some background, from the online exhibit:

In the spring of 2006 we again asked the Princeton University community to submit images—and, for the first time, videos and sounds—produced in the course of research or incorporating tools and concepts from science. Out of nearly 150 entries from 16 departments, we selected 56 works to appear in the 2006 Art of Science exhibition.

The practices of science and art both involve the single-minded pursuit of those moments of discovery when what one perceives suddenly becomes more than the sum of its parts. Each piece in this exhibition is, in its own way, a record of such a moment. They range from the image that validates years of research, to the epiphany of beauty in the trash after a long day at the lab, to a painter’s meditation on the meaning of biological life.

You can view the exhibit online, but the best way to see it is in person, in the main hallway of the Friend Center on the Princeton campus. One of the highlights is outdoors: a fascinating metal object that looks for all the world like a modernist sculpture but was actually built as a prototype winding coil for a giant electromagnet that will control superhot plasma in a fusion energy experiment. (The online photo doesn’t do it justice.)

If you’re on the Princeton campus on Friday afternoon (June 2), you’ll want to see the panel discussion on “Privacy and Security in the Digital Age”, which I’ll be moderating. We have an all-star group of panelists:
* Dave Hitz (Founder, Network Appliance)
* Paul Misener (VP for Global Public Affairs, Amazon)
* Harriet Pearson (Chief Privacy Officer, IBM)
* Brad Smith (Senior VP and General Counsel, Microsoft)
It’s in 006 Friend, just downstairs from the Art of Science exhibit, from 2:00 to 3:00 on Friday.

These panelists are just a few of the distinguished Princeton alumni who will be on campus this weekend for Reunions.

Zfone Encrypts VoIP Calls

Phil Zimmerman, who created the PGP encryption software, and faced a government investigation as a result, now offers a new program, Zfone, that provides end-to-end encryption of computer-to-computer (VoIP) phone calls, according to a story in yesterday’s New York Times.

One of the tricky technical problems in encrypting communications is key exchange: how to get the two parties to agree on a secret key that only they know. This is often done with a cumbersome “public key infrastructure” (PKI), which wouldn’t work well for this application. Zfone has a clever key exchange protocol that dispenses with the PKI and instead relies on the two people reading short character strings to each other over the voice connection. This will provide a reasonably secure shared secret key, as long as the two people recognize each others’ voices.

(Homework problem for security students: What does the string-reading accomplish? Based on just the information here, how do you think the Zfone key exchange protocol works?)

In the middle of the article is this interesting passage:

But Mr. Zimmermann, 52, does not see those fearing government surveillance — or trying to evade it — as the primary market [for Zfone]. The next phase of the Internet’s spyware epidemic, he contends, will be software designed to eavesdrop on Internet telephone calls made by corporate users.

“They will have entire digital jukeboxes of covertly acquired telephone conversations, and suddenly someone in Eastern Europe is going to be very wealthy,” he said.

Though the article doesn’t say so directly, this passage seems to imply that Zfone can protect against spyware-based eavesdropping. That’s not right.

One of the challenges in using encryption is that the datastream is not protected before it is encrypted at the source, or after it is decrypted at the destination. If you and I are having a Zfone-protected conversation, spyware on your computer could capture your voice before it is encrypted for transmission to me, and could also capture my voice after it is decrypted on your computer. Zfone is helpless against this threat, as are other VoIP encryption schemes.

All of this points to an interesting consequence of strong encryption. As more and more communications are strongly encrypted, would-be spies have less to gain from wiretapping and more to gain from injecting malware into their targets’ computers. Yet another reason to expect a future with even more malware.

NYU/Princeton Spyware Workshop Liveblog

Today I’m at the NYU/Princeton spyware workshop. I’ll be liveblogging the workshop here. I won’t give you copious notes on what each speaker says, just a list of things that strike me as interesting. Videos of the presentations will be available on the net eventually.

I gave a basic tutorial on spyware last night, to kick off the workshop.

The first panel today is officially about the nature of the spyware problem, but it’s shaping up as the law enforcement panel. The first speaker is Mark Eckenwiler from the U.S. Department of Justice. He is summarizing the various Federal statutes that can be used against spyware purveyors, including statutes against wiretapping and computer intrusions. One issue I hadn’t heard before involves how to prove that a particular spyware purveyor caused harm, if the victim’s computer was also infected with lots of other spyware from other sources.

Second speaker is Eileen Harrington of the Federal Trade Commission. The FTC has two main roles here: to enforce laws, especially relating to unfair and deceptive business practices, and to run hearings and study issues. In 1995 the FTC ran a series of hearing on online consumer protection, which identified privacy as important but didn’t identify spam or spyware. In recent years their focus has shifted more toward spyware. FTC enforcement is based on three principles: the computer belongs to the consumer; disclosure can’t be buried in a EULA; and software must be reasonably removable. These seem sensible to me. She recommends a consumer education website created by the FTC and other government agencies.

Third speaker is Justin Brookman of the New York Attorney General’s office. To them, consent is the biggest issue. He is skeptical of state spyware laws, saying they are often too narrow and require high level of intent to be proven for civil liability. Instead, they enforce based on laws against deceptive business practices and false advertising, and on trespass to chattels. They focus on the consumer experience, and don’t always need to dig very deeply into all of the technical details. He says music lyric sites are often spyware-laden. In one case, a screen saver came with a 188-page EULA, which mentioned the included adware on page 131. He raises the issue of when companies are responsible for what their “affiliates” do.

Final speaker of the first panel is Ari Schwartz of CDT, who runs the Anti-Spyware Coalition. ASC is a big coalition of public-interest groups, companies, and others to build consensus around a definition of spyware and principles for dealing with it. The definition problem is both harder and more important than you might think. The goal was to create a broadly accepted definition, to short-circuit debates about whether particular pieces of unpleasant software are or are not spyware. He says that many of the harms caused by software are well addressed by existing law (identity theft, extortion, corporate espionage, etc.), but general privacy invasions are not. In what looks like a recurring theme for the workshop, he talks about how spyware purveyors use intermediaries (“affiliates”) to create plausible deniability. He shows a hair-raising chain of emails obtained in discovery in an FTC case against Sanford Wallace and associates. This was apparently an extortion-type scheme, where extreme spyware was locked on to a user’s computer, and the antidote was sold to users for $30.

Question to the panel about what happens if the perpetrator is overseas. Eileen Harrington says that if there are money flows, they can freeze assets or sometimes get money repatriated for overseas. The FTC wants statutory changes to foster information exchange with other governments. Ari Schwartz says advertisers, ad agencies, and adware makers are mostly in the U.S. Distribution of software is sometimes from the U.S., sometimes from Eastern Europe, former Soviet Union, or Asia.

Q&A discussion of how spyware programs attack each other. Justin Brookman talks about a case where one spyware company sued another spyware company over this.

The second panel is on “motives, incentives, and causes”. It’s two engineers and two lawyers. First is Eric Allred, an engineer from Microsoft’s antispyware group. “Why is this going on? For the money.”

Eric talks about game programs that use spyware tactics to fight cheating code, e.g. the “warden” in World of Warcraft. He talks about products that check quality of service or performance provided by, e.g., network software, by tracking some behaviors. He thinks this is okay with adequate notice and consent.

He takes a poll of the room. Only a few people admit to having their machines infected by spyware – I’ll bet people are underreporting. Most people say that friends have caught spyware.

Second speaker is Markus Jakobsson, an engineer from Indiana University and RavenWhite. He is interested in phishing and pharming, and the means by which sites can gather information about you. As a demonstration, he says his home page tells you where you do your online banking.

He describes an experiment they did that simulated phishing against IU students. Lots of people fell for it. Interestingly, people with political views on the far left or far right were more likely to fall for it than people with more moderate views. The experimental subjects were really mad (but the experiment had proper institutional review board approval).

“My conclusion is that user education does not work.”

Third is Paul Ohm, a law professor at Colorado. He was previously a prosecutor at the DOJ. He talks about the “myth of the superuser”. (I would have said “superattacker”.) He argues that Internet crime policy is wrongly aimed to stop the superuser.

What happens? Congress writes prohibitions that are broad and vague. Prosecutors and civil litigants use the broad language to pursue novel theories. Innocent people get swept in.

He conjectures that most spyware purveyors aren’t technological superuser. In general, he argues that legislation should focus on non-superuser methods and harms.

He talks about the SPYBLOCK Act language, which bans certain actions, if done with certain bad intent. “The FBI agent stops reading after the list of actions.”

Fourth is Marc Rotenberg from EPIC. His talk is structured as a list of observations, presented in random order. I’ll repeat some of them here. (1) People tend to behave opportunistically online – extract information if you can. (2) “Spyware is a crime of architectural opportunity.” (3) Motivations for spyware: money, control, exploitation, investigation.

He argues that cookies are spyware. This is a controversial view. He argues for reimagining cookies or how users can control them.

Q&A session begins. Alex asks Paul Ohm whether it makes sense in the long run to focus on attackers who aren’t super, given that attackers can adapt. Paul says, first, that he hopes technologists will help stop the superattackers. (The myth of the super-defender?) He advocates a more incremental and adaptive approach to drafting the statutes; aim at the 80% case, then adjust every few years.

Question to Marc Rotenberg about what can be done about cookies. Marc says that originally cookies contained, legibly, the information they represented, such as your zip code. But before long cookies morphed into unique identifiers, opaque to the user. Eric Allred points out that the cookies can be strongly, cryptographically opaque to users.

The final session is on solutions. Ben Edelman speaks first. He shows a series of examples of unsavory practices, relating to installation without full consent and to revenue sources for adware.

He shows a scenario where a NetFlix popup ad appears when a user visits blockbuster.com. This happened through a series of intermediaries – seven HTTP redirects – to pop up the ad. Netflix paid LinkShare, LinkShare paid Azoogle, Azoogle paid MyGeek, and MyGeek paid DirectRevenue. He’s got lots of examples like this, from different mainstream ad services.

He shows an example of Google AdSense ads popping up in 180solutions adware popup windows. He says he found 4600+ URLs where this happened (as of last June).

Orin Kerr speaks next. “The purpose of my talk is to suggest that there are no good ways for the law to handle the spyware problem.” He suggests that technical solutions are a better idea. A pattern today: lawyers want to rely more on technical solutions, technologists want to rely more on law.

He says criminal law works best when the person being prosecuted is clearly evil, even to a juror who doesn’t understand much about what happened. He says that spyware purveyors more often operate in a hazy gray area – so criminal prosecution doesn’t look like the right tool.

He says civil suits by private parties may not work, because defendants don’t have deep enough pockets to make serious suits worthwhile.

He says civil suits by government (e.g., the FTC) may not work, because they have weaker investigative powers than criminal investigators, especially against fly-by-night companies.

It seems to me that his arguments mostly rely on the shady, elusive nature of spyware companies. Civil actions may work against large companies that portray themselves as legitimate. So they may have the benefit of driving spyware vendors underground, which could make it harder for them to sell to some advertisers.

Ira Rubinstein of Microsoft is next. His title is “Code Signing As a Spyware Solution”. He describes (the 64-bit version of) Windows Vista, which will require any kernel-mode software to be digitally signed. This is aimed to stop rootkits and other kernel-mode exploits. It sounds quite similar to AuthentiCode, Microsoft’s longstanding signing infrastructure for ActiveX controls.

Mark Miller of HP is the last speaker. His talk starts with an End-User Listening Agreement, in which everyone in the audience must agree that he can read our minds and redistribute what he learns. He says that we’re not concerned about this because it’s infeasible for him to install hostile code into our brains.

He points out that the Solitaire program has the power to read, analyze or transmit any data on the computer. Any other program can do the same. He argues that we need to obey the principle of least privilege. It seems to me that we already have all the tools to do this, but people don’t do it.

He shows an example of how to stop a browser from leaking your secrets, by either not letting it connect to the Net, or not letting it read any local files. But even a simple browser needs to do both. This is not a convincing demo.

In the Q&A, Ben Edelman recommend’s Eric Howes’s web site as a list of which antispyware tools are legit and which are bogus or dangerous.

Orin Kerr is asked whether we should just give up on using the law. He says no, we should use the law to chip away at the problem, but we shouldn’t expect it to solve the problem entirely. Justin Brookman challenges Orin, saying that civil subpoenia power seems to work for Justin’s group at the NY AG office. Orin backtracks slightly but sticks to his basic point that spyware vendors will adapt or evolve into forms more resistant to enforcement.

Alex asks Orin how law and technology might work together to attack the problem. Orin says he doesn’t see a grand solution, just incremental chipping away at the problem. Ira Rubinstein says that law can adjust incentives, to foster adoption of better technology approaches.

And our day draws to a close. All in all, it was a very interesting and thought-provoking discussion. I wish it had been longer – which I rarely say at the end of this kind of event.

RFID Virus Predicted

Melanie Rieback, Bruno Crispo, and Andy Tanenbaum have a new paper describing how RFID tags might be used to propagate computer viruses. This has garnered press coverage, including a John Markoff story in today’s New York Times.

The underlying technical argument is pretty simple. An RFID tag is a tiny device, often affixed to a product of some sort, that carries a relatively small amount of data. An RFID reader is a larger device, often stationary, that can use radio signals to read and/or modify the contents of RFID tags. In a retail application, a store might affix an RFID tag to each item in stock, and have an RFID reader at each checkout stand. A customer could wheel a shopping cart full of items up to the checkout stand, and the RFID reader would determine which items were in the cart and would charge the customer and adjust the store’s inventory database accordingly.

Simple RFID tags are quite simple and only carry data that can be read or modified by readers. Tags cannot themselves be infected by viruses. But they can act as carriers, as I’ll describe below.

RFID readers, on the other hand, are often quite complicated and interact with networked databases. In our retail example, each RFID reader can connect to the store’s backend databases, in order to update the store’s inventory records. If RFID readers run complicated software, then they will inevitably have bugs.

One common class of bugs involves bad handling of unexpected or diabolical input values. For example, web browsers have had bugs in their URL-handling code, which caused the browsers to either crash or be hijacked when they encountered diabolically constructed URLs. When such a bug existed, an attacker who could present an evil URL to the browser (for example, by getting the user to navigate to it) could seize control of the browser.

Suppose that some subset of the world’s RFID readers had an input-processing bug of this general type, so that whenever one of these readers scanned an RFID tag containing diabolically constructed input, the reader would be hijacked and would execute some command contained in that input. If this were the case, an RFID-carried virus would be possible.

A virus attack might start with a single RFID tag carrying evil data. When a vulnerable reader scanned that tag, the reader’s bug would be triggered, causing the reader to execute a command specified by that tag. The command would reconfigure the reader to make it write copies of the evil data onto tags that it saw in the future. This would spread the evil data onto more tags. When any of those tags came in contact with a vulnerable reader, that reader would be infected, turning it into a factory for making more infected tags. The infection would spread from readers to new tags, and from tags to new readers. Before long many tags and readers would be infected.

To demonstrate the plausibility of this scenario, the researchers wrote their own RFID reader, giving it a common type of bug called an SQL injection vulnerability. They then constructed the precise diabolical data needed to exploit that vulnerability, and demonstrated that it would spread automatically as described. In light of this demo, it’s clear that RFID viruses can exist, if RFID readers have certain types of bugs.

Do such bugs exist in real RFID readers? We don’t know – the researchers don’t point to any – but it is at least plausible that such bugs will exist. Our experience with Web and Internet software is not encouraging in this regard. Bugs can be avoided by very careful engineering. But will engineers be so careful? Not always. We don’t know how common RFID viruses will be, but it seems likely they will exist in the wild, eventually.

Designers of RFID-based systems will have to engineer their systems much more carefully than we had previously thought necessary.