Original URL: http://www.theregister.co.uk/2008/09/26/boston_mta_hack/

The Boston Trio and the MBTA

How the transport bods silenced security researchers

By Mark Rasch

Posted in Security, 26th September 2008 10:26 GMT

The annual DEFCON conference in Las Vegas in early August got a bit more interesting than usual when three graduate students from the Massachusetts Institute of Technology were enjoined from giving a presentation by a court in Boston.

The three - Zach Anderson, RJ Ryan and Alessandro Chiesa - intended to present both a paper and slides to the assembled masses of hackers explaining certain configuration issues with respect to the Massachusetts Bay Transportation Authority (MBTA) fare card system for riding the Boston subway system. The fare card system, or Fare Media system, used stored value cards, known as CharlieCards, after a locally famous song by the Kingston Trio called Charlie on the MTA.

Let me tell you the story
Of some boys from MIT
On a tragic and fateful day
They put out some information
Kissed their career and reputation
And took for ride the MTA

The cards were subject to various cloning attacks, which would permit both sophisticated and unsophisticated hackers to create duplicate CharlieCards, and therefore evade payment for subway rides.

Needless to say, when the lawyers for the MBTA learned of the DEFCON presentation, they were not amused. While there are disputes about who contacted whom first, and precisely what information was going to be disclosed or not disclosed at the presentation, ultimately the MBTA went to court in Boston and obtained a temporary restraining order (TRO) preventing the release of certain information about the vulnerabilities. The TRO was eventually reversed by the court, but not until the trio was denied the opportunity to make their presentation. Of course, in keeping with the Streisand effect, where attempts to censor content merely draws attention to it, both the slides and the paper to be presented were widely disseminated in advance of the TRO.

Much of the debate over the TRO has focused on the prior restraint on free speech aspects of the case. However, more important to security researchers are the questions of responsible or irresponsible disclosure of security vulnerabilities, and potential civil or criminal liability for doing so.

Security Research as a crime?

In their efforts to get a court to keep the MIT students from disclosing the results of their research, lawyers for the MBTA argued (pdf) not simply that the release of this information would harm the mass transit system, but also that the actions of the undergrads was criminal. Yet, everybody seems to have acknowledged that the information was not obtained by the undergraduates unlawfully - that is, they didn't steal it, and didn't violate trade secrets to get it.

Did they ever return,
No they never returned
And their ultimate fates still unlearn'd
They may try forever
In the courts of Boston
They're the kids who never returned.

So what was the MIT students' crime? Apparently nothing more than telling people about the vulnerabilities.

When the first US federal computer crime statute was written, it punished things like computer trespass and theft of electronic services or information. After the Cornell Internet Worm case in 1988, Congress added a provision to explicitly criminalize computer viruses. This provision made it a crime to:

Knowingly cause the transmission of a program, information, code, or command, and as a result of such conduct, intentionally causes damage without authorization, to a protected computer; which causes or would have caused loss of more than $5,000.

When Congress was considering this provision, at least one influential member of Congress made it clear that "transmission does not refer [to] speech or other forms of communication to human beings" (pdf).

From the subway system's perspective, the MIT students learned information about vulnerabilities in the system's computers - whether these "computers" are the MBTA's system, the machines that process the subway fare cards, or even the stored value RFID fare cards themselves. When they tell the public about this vulnerability - by describing the flaw, describing an exploit, or releasing code - they have "transmitted information". If, as a result of this transmission of information someone then causes damage or might cause damage to the computer which might cause economic loss, then the person who transmitted the information is liable.

The evidence that the students intended to cause damage to the MBTA's computers is contained in the fact that they promoted their presentation by telling people that they had found a way to get free subway rides. Indeed, the MBTA alleged that the students had already committed a crime based upon audit evidence that the students may have tested one of their modified or cloned fare cards.

The MBTA next argues that, by transmitting this information at DEFCON, a hacker conference, the student's actions are "directed at and likely to incite imminent lawless action". By telling others - or threatening to tell others - about the vulnerabilities, the students are, according to the mass transit system, aiding and abetting potential crimes which might be later committed by these others. The MBTA finally argues that even showing a picture of an MBTA switch with a mention of the network analyzer tool Wireshark is the felonious encouragement of criminal activity.

Responsible Disclosure

Now I am all for responsible disclosure of vulnerabilities. I will venture no opinion here about whether the MIT students here made disclosures to MBTA in a responsible way - that is, whether they gave the MBTA enough time and information to effectively address the configurations and/or vulnerabilities, and this seems to be the parties' main point of contention.

However, there exists a Constitutional right to irresponsibly disclose a vulnerability, if there was no crime committed in learning about the issue.

Imagine this scenario: A man in a ski mask asks you if you know how to break into the vault at the local savings and loan. Being a security expert, you provide this unknown person with detailed information about the configuration of the bank's security system. The masked man then uses this information to break in. In that scenario, you may be liable as an "aider and abetter" of the ultimate crime, as a criminal facilitator or as a co-conspirator. The issue here is one of mental state and intent. Do you intend to help someone commit a crime? Do you "conspire, confederate, and agree" with someone to make their crime happen? Or are you merely - responsibly or not - doing something which the real criminal finds useful?

Similarly, there clearly is a distinction between launching a virus, posting a virus that others may launch, posting uncompiled code about how to make a virus, and writing an academic paper about how viruses work. While all of these may be used to cause damage to a computer system, there are issues of immediacy and causality.

The law tends to punish both intent, or mens rea, and actions, or actus reas. While the MIT students clearly could have known that the black-hat hackers would find the released information at least useful in committing a crime - getting free subway rides - it is doubtful that they could be said to have intended to cause actual damage to the computers.

Indeed, Jennifer Granick, the lawyer representing the three MIT students had previously and successfully represented Bret McDanel, who was criminally prosecuted by the government under the same flawed reading of the computer crime statute. After McDanel, known as "Secret Squirrel" was tried, convicted and sentenced for telling people how to read other people's email on a supposedly "secure" system, and after he served his sixteen-month sentence, Granick convinced the prosecutors that their theory of prosecution - that is, merely disclosing a vulnerability is a crime - was flawed, and the government dismissed the charges against McDanel. It was this same theory that was resurrected by the MBTA, and convinced at least one federal magistrate.

As the trains rolled on
underneath Greater Boston
The students looked around and sighed:
"Well, we're sore and disgusted
And we're absolutely busted;
I guess this is our last free ride.

Whenever security researchers release hitherto undisclosed information that could be used to cause harm, damage or loss, they run the risk of civil or criminal exposure, and to possible overreaction. What the MBTA probably wanted was just more time to evaluate the vulnerability and fix it before an exploit could be propagated. It is unlikely, however, that the First Amendment mandated that the MIT students provide it.

This article originally appeared in Security Focus.

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