Schneier on Security
A blog covering security and security technology.
October 1, 2004
Keeping Network Outages Secret
There's considerable confusion between the concept of secrecy and the concept of security, and it is causing a lot of bad security and some surprising political arguments. Secrecy is not the same as security, and most of the time secrecy contributes to a false feeling of security instead of to real security.
In June, the U.S. Department of Homeland Security urged regulators to keep network outage information secret. The Federal Communications Commission already requires telephone companies to report large disruptions of telephone service, and wants to extend that requirement to high-speed data lines and wireless networks. But the DHS fears that such information would give cyberterrorists a "virtual road map" to target critical infrastructures.
This sounds like the "full disclosure" debate all over again. Is publishing computer and network vulnerability information a good idea, or does it just help the hackers? It arises again and again, as malware takes advantage of software vulnerabilities after they've been made public.
The argument that secrecy is good for security is naive, and always worth rebutting. Secrecy is only beneficial to security in limited circumstances, and certainly not with respect to vulnerability or reliability information. Secrets are fragile; once they're lost they're lost forever. Security that relies on secrecy is also fragile; once secrecy is lost there's no way to recover security. Trying to base security on secrecy is just plain bad design.
Cryptography is based on secrets -- keys -- but look at all the work that goes into making them effective. Keys are short and easy to transfer. They're easy to update and change. And the key is the only secret component of a cryptographic system. Cryptographic algorithms make terrible secrets, which is why one of cryptography's most basic principles is to assume that the algorithm is public.
That's the other fallacy with the secrecy argument: the assumption that secrecy works. Do we really think that the physical weak points of networks are such a mystery to the bad guys? Do we really think that the hacker underground never discovers vulnerabilities?
Proponents of secrecy ignore the security value of openness: public scrutiny is the only reliable way to improve security. Before software bugs were routinely published, software companies routinely denied their existence and wouldn't bother fixing them, believing in the security of secrecy. And because customers didn't know any better, they bought these systems, believing them to be secure. If we return to a practice of keeping software bugs secret, we'll have vulnerabilities known to a few in the security community and to much of the hacker underground.
Secrecy prevents people from assessing their own risks.
Public reporting of network outages forces telephone companies to improve their service. It allows consumers to compare the reliability of different companies, and to choose one that best serves their needs. Without public disclosure, companies could hide their reliability performance from the public.
Just look at who supports secrecy. Software vendors such as Microsoft want very much to keep vulnerability information secret. The Department of Homeland Security's recommendations were loudly echoed by the phone companies. It's the interests of these companies that are served by secrecy, not the interests of consumers, citizens, or society.
In the post-9/11 world, we're seeing this clash of secrecy versus openness everywhere. The U.S. government is trying to keep details of many anti-terrorism countermeasures -- and even routine government operations -- secret. Information about the infrastructure of plants and government buildings is secret. Profiling information used to flag certain airline passengers is secret. The standards for the Department of Homeland Security's color-coded terrorism threat levels are secret. Even information about government operations without any terrorism connections is being kept secret.
This keeps terrorists in the dark, especially "dumb" terrorists who might not be able to figure out these vulnerabilities on their own. But at the same time, the citizenry -- to whom the government is ultimately accountable -- is not allowed to evaluate the countermeasures, or comment on their efficacy. Security can't improve because there's no public debate or public education.
Recent studies have shown that most water, power, gas, telephone, data, transportation, and distribution systems are scale-free networks. This means they always have highly connected hubs. Attackers know this intuitively and go after the hubs. Defenders are beginning to learn how to harden the hubs and provide redundancy among them. Trying to keep it a secret that a network has hubs is futile. Better to identify and protect them.
We're all safer when we have the information we need to exert market pressure on vendors to improve security. We would all be less secure if software vendors didn't make their security vulnerabilities public, and if telephone companies didn't have to report network outages. And when government operates without accountability, that serves the security interests of the government, not of the people.
Another version of this essay appeared in the October Communications of the ACM.
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