Entries Tagged "essays"

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Unauthentication

In computer security, a lot of effort is spent on the authentication problem. Whether it’s passwords, secure tokens, secret questions, image mnemonics, or something else, engineers are continually coming up with more complicated—and hopefully more secure—ways for you to prove you are who you say you are over the Internet.

This is important stuff, as anyone with an online bank account or remote corporate network knows. But a lot less thought and work have gone into the other end of the problem: how do you tell the system on the other end of the line that you’re no longer there? How do you unauthenticate yourself?

My home computer requires me to log out or turn my computer off when I want to unauthenticate. This works for me because I know enough to do it, but lots of people just leave their computers on and running when they walk away. As a result, many office computers are left logged in when people go to lunch, or when they go home for the night. This, obviously, is a security vulnerability.

The most common way to combat this is by having the system time out. I could have my computer log me out automatically after a certain period of inactivity—five minutes, for example. Getting it right requires some fine tuning, though. Log the person out too quickly, and he gets annoyed; wait too long before logging him out, and the system could be vulnerable during that time. My corporate e-mail server logs me out after 10 minutes or so, and I regularly get annoyed at my corporate e-mail system.

Some systems have experimented with a token: a USB authentication token that has to be plugged in for the computer to operate, or an RFID token that logs people out automatically when the token moves more than a certain distance from the computer. Of course, people will be prone to just leave the token plugged in to their computer all the time; but if you attach it to their car keys or the badge they have to wear at all times when walking around the office, the risk is minimized.

That’s expensive, though. A research project used a Bluetooth device, like a cellphone, and measured its proximity to a computer. The system could be programmed to lock the computer if the Bluetooth device moved out of range.

Some systems log people out after every transaction. This wouldn’t work for computers, but it can work for ATMs. The machine spits my card out before it gives me my cash, or just requires a card swipe, and makes sure I take it out of the machine. If I want to perform another transaction, I have to reinsert my card and enter my PIN a second time.

There’s a physical analogue that everyone can explain: door locks. Does your door lock behind you when you close the door, or does it remain unlocked until you lock it? The first instance is a system that automatically logs you out, and the second requires you to log out manually. Both types of locks are sold and used, and which one you choose depends on both how you use the door and who you expect to try to break in.

Designing systems for usability is hard, especially when security is involved. Almost by definition, making something secure makes it less usable. Choosing an unauthentication method depends a lot on how the system is used as well as the threat model. You have to balance increasing security with pissing the users off, and getting that balance right takes time and testing, and is much more an art than a science.

This essay originally appeared on ThreatPost.

Posted on September 28, 2009 at 1:34 PM • View Comments

File Deletion

File deletion is all about control. This used to not be an issue. Your data was on your computer, and you decided when and how to delete a file. You could use the delete function if you didn’t care about whether the file could be recovered or not, and a file erase program—I use BCWipe for Windows—if you wanted to ensure no one could ever recover the file.

As we move more of our data onto cloud computing platforms such as Gmail and Facebook, and closed proprietary platforms such as the Kindle and the iPhone, deleting data is much harder.

You have to trust that these companies will delete your data when you ask them to, but they’re generally not interested in doing so. Sites like these are more likely to make your data inaccessible than they are to physically delete it. Facebook is a known culprit: actually deleting your data from its servers requires a complicated procedure that may or may not work. And even if you do manage to delete your data, copies are certain to remain in the companies’ backup systems. Gmail explicitly says this in its privacy notice.

Online backups, SMS messages, photos on photo sharing sites, smartphone applications that store your data in the network: you have no idea what really happens when you delete pieces of data or your entire account, because you’re not in control of the computers that are storing the data.

This notion of control also explains how Amazon was able to delete a book that people had previously purchased on their Kindle e-book readers. The legalities are debatable, but Amazon had the technical ability to delete the file because it controls all Kindles. It has designed the Kindle so that it determines when to update the software, whether people are allowed to buy Kindle books, and when to turn off people’s Kindles entirely.

Vanish is a research project by Roxana Geambasu and colleagues at the University of Washington. They designed a prototype system that automatically deletes data after a set time interval. So you can send an email, create a Google Doc, post an update to Facebook, or upload a photo to Flickr, all designed to disappear after a set period of time. And after it disappears, no one—not anyone who downloaded the data, not the site that hosted the data, not anyone who intercepted the data in transit, not even you—will be able to read it. If the police arrive at Facebook or Google or Flickr with a warrant, they won’t be able to read it.

The details are complicated, but Vanish breaks the data’s decryption key into a bunch of pieces and scatters them around the web using a peer-to-peer network. Then it uses the natural turnover in these networks—machines constantly join and leave—to make the data disappear. Unlike previous programs that supported file deletion, this one doesn’t require you to trust any company, organisation, or website. It just happens.

Of course, Vanish doesn’t prevent the recipient of an email or the reader of a Facebook page from copying the data and pasting it into another file, just as Kindle’s deletion feature doesn’t prevent people from copying a book’s files and saving them on their computers. Vanish is just a prototype at this point, and it only works if all the people who read your Facebook entries or view your Flickr pictures have it installed on their computers as well; but it’s a good demonstration of how control affects file deletion. And while it’s a step in the right direction, it’s also new and therefore deserves further security analysis before being adopted on a wide scale.

We’ve lost the control of data on some of the computers we own, and we’ve lost control of our data in the cloud. We’re not going to stop using Facebook and Twitter just because they’re not going to delete our data when we ask them to, and we’re not going to stop using Kindles and iPhones because they may delete our data when we don’t want them to. But we need to take back control of data in the cloud, and projects like Vanish show us how we can.

Now we need something that will protect our data when a large corporation decides to delete it.

This essay originally appeared in The Guardian.

EDITED TO ADD (9/30): Vanish has been broken, paper here.

Posted on September 10, 2009 at 6:08 AM • View Comments

Real-World Access Control

Access control is difficult in an organizational setting. On one hand, every employee needs enough access to do his job. On the other hand, every time you give an employee more access, there’s more risk: he could abuse that access, or lose information he has access to, or be socially engineered into giving that access to a malfeasant. So a smart, risk-conscious organization will give each employee the exact level of access he needs to do his job, and no more.

Over the years, there’s been a lot of work put into role-based access control. But despite the large number of academic papers and high-profile security products, most organizations don’t implement it—at all—with the predictable security problems as a result.

Regularly we read stories of employees abusing their database access-control privileges for personal reasons: medical records, tax records, passport records, police records. NSA eavesdroppers spy on their wives and girlfriends. Departing employees take corporate secrets

A spectacular access control failure occurred in the UK in 2007. An employee of Her Majesty’s Revenue & Customs had to send a couple of thousand sample records from a database on all children in the country to National Audit Office. But it was easier for him to copy the entire database of 25 million people onto a couple of disks and put it in the mail than it was to select out just the records needed. Unfortunately, the discs got lost in the mail and the story was a huge embarrassment for the government.

Eric Johnson at Dartmouth’s Tuck School of Business has been studying the problem, and his results won’t startle anyone who has thought about it at all. RBAC is very hard to implement correctly. Organizations generally don’t even know who has what role. The employee doesn’t know, the boss doesn’t know—and these days the employee might have more than one boss—and senior management certainly doesn’t know. There’s a reason RBAC came out of the military; in that world, command structures are simple and well-defined.

Even worse, employees’ roles change all the time—Johnson chronicled one business group of 3,000 people that made 1,000 role changes in just three months—and it’s often not obvious what information an employee needs until he actually needs it. And information simply isn’t that granular. Just as it’s much easier to give someone access to an entire file cabinet than to only the particular files he needs, it’s much easier to give someone access to an entire database than only the particular records he needs.

This means that organizations either over-entitle or under-entitle employees. But since getting the job done is more important than anything else, organizations tend to over-entitle. Johnson estimates that 50 percent to 90 percent of employees are over-entitled in large organizations. In the uncommon instance where an employee needs access to something he normally doesn’t have, there’s generally some process for him to get it. And access is almost never revoked once it’s been granted. In large formal organizations, Johnson was able to predict how long an employee had worked there based on how much access he had.

Clearly, organizations can do better. Johnson’s current work involves building access-control systems with easy self-escalation, audit to make sure that power isn’t abused, violation penalties (Intel, for example, issues “speeding tickets” to violators), and compliance rewards. His goal is to implement incentives and controls that manage access without making people too risk-averse.

In the end, a perfect access control system just isn’t possible; organizations are simply too chaotic for it to work. And any good system will allow a certain number of access control violations, if they’re made in good faith by people just trying to do their jobs. The “speeding ticket” analogy is better than it looks: we post limits of 55 miles per hour, but generally don’t start ticketing people unless they’re going over 70.

This essay previously appeared in Information Security, as part of a point/counterpoint with Marcus Ranum. You can read Marcus’s response here—after you answer some nosy questions to get a free account.

Posted on September 3, 2009 at 12:54 PM • View Comments

Self-Enforcing Protocols

There are several ways two people can divide a piece of cake in half. One way is to find someone impartial to do it for them. This works, but it requires another person. Another way is for one person to divide the piece, and the other person to complain (to the police, a judge, or his parents) if he doesn’t think it’s fair. This also works, but still requires another person—at least to resolve disputes. A third way is for one person to do the dividing, and for the other person to choose the half he wants.

That third way, known by kids, pot smokers, and everyone else who needs to divide something up quickly and fairly, is called cut-and-choose. People use it because it’s a self-enforcing protocol: a protocol designed so that neither party can cheat.

Self-enforcing protocols are useful because they don’t require trusted third parties. Modern systems for transferring money—checks, credit cards, PayPal—require trusted intermediaries like banks and credit card companies to facilitate the transfer. Even cash transfers require a trusted government to issue currency, and they take a cut in the form of seigniorage. Modern contract protocols require a legal system to resolve disputes. Modern commerce wasn’t possible until those systems were in place and generally trusted, and complex business contracts still aren’t possible in areas where there is no fair judicial system. Barter is a self-enforcing protocol: nobody needs to facilitate the transaction or resolve disputes. It just works.

Self-enforcing protocols are safer than other types because participants don’t gain an advantage from cheating. Modern voting systems are rife with the potential for cheating, but an open show of hands in a room—one that everyone in the room can count for himself—is self-enforcing. On the other hand, there’s no secret ballot, late voters are potentially subjected to coercion, and it doesn’t scale well to large elections. But there are mathematical election protocols that have self-enforcing properties, and some cryptographers have suggested their use in elections.

Here’s a self-enforcing protocol for determining property tax: the homeowner decides the value of the property and calculates the resultant tax, and the government can either accept the tax or buy the home for that price. Sounds unrealistic, but the Greek government implemented exactly that system for the taxation of antiquities. It was the easiest way to motivate people to accurately report the value of antiquities.

A VAT, or value-added tax, is a self-enforcing alternative to sales tax. Sales tax is collected on the entire value of the thing at the point of retail sale; both the customer and the storeowner want to cheat the government. But VAT is collected at every step between raw materials and that final customer; it’s the difference between the price of the materials sold and the materials bought. Buyers wants official receipts with as high a purchase price as possible, so each buyer along the chain keeps each seller honest. Yes, there’s still an incentive to cheat on the final sale to the customer, but the amount of tax collected at that point is much lower.

Of course, self-enforcing protocols aren’t perfect. For example, someone in a cut-and-choose can punch the other guy and run away with the entire piece of cake. But perfection isn’t the goal here; the goal is to reduce cheating by taking away potential avenues of cheating. Self-enforcing protocols improve security not by implementing countermeasures that prevent cheating, but by leveraging economic incentives so that the parties don’t want to cheat.

One more self-enforcing protocol. Imagine a pirate ship that encounters a storm. The pirates are all worried about their gold, so they put their personal bags of gold in the safe. During the storm, the safe cracks open, and all the gold mixes up and spills out on the floor. How do the pirates determine who owns what? They each announce to the group how much gold they had. If the total of all the announcements matches what’s in the pile, it’s divided as people announced. If it’s different, then the captain keeps it all. I can think of all kinds of ways this can go wrong—the captain and one pirate can collude to throw off the total, for example—but it is self-enforcing against individual misreporting.

This essay originally appeared on ThreatPost.

EDITED TO ADD (8/12): Shotgun clauses are an example of a self-enforcing protocol.

Posted on August 11, 2009 at 6:15 AM • View Comments

Risk Intuition

People have a natural intuition about risk, and in many ways it’s very good. It fails at times due to a variety of cognitive biases, but for normal risks that people regularly encounter, it works surprisingly well: often better than we give it credit for.

This struck me as I listened to yet another conference presenter complaining about security awareness training. He was talking about the difficulty of getting employees at his company to actually follow his security policies: encrypting data on memory sticks, not sharing passwords, not logging in from untrusted wireless networks. “We have to make people understand the risks,” he said.

It seems to me that his co-workers understand the risks better than he does. They know what the real risks are at work, and that they all revolve around not getting the job done. Those risks are real and tangible, and employees feel them all the time. The risks of not following security procedures are much less real. Maybe the employee will get caught, but probably not. And even if he does get caught, the penalties aren’t serious.

Given this accurate risk analysis, any rational employee will regularly circumvent security to get his or her job done. That’s what the company rewards, and that’s what the company actually wants.

“Fire someone who breaks security procedure, quickly and publicly,” I suggested to the presenter. “That’ll increase security awareness faster than any of your posters or lectures or newsletters.” If the risks are real, people will get it.

You see the same sort of risk intuition on motorways. People are less careful about posted speed limits than they are about the actual speeds police issue tickets for. It’s also true on the streets: people respond to real crime rates, not public officials proclaiming that a neighbourhood is safe.

The warning stickers on ladders might make you think the things are considerably riskier than they are, but people have a good intuition about ladders and ignore most of the warnings. (This isn’t to say that some people don’t do stupid things around ladders, but for the most part they’re safe. The warnings are more about the risk of lawsuits to ladder manufacturers than risks to people who climb ladders.)

As a species, we are naturally tuned in to the risks inherent in our environment. Throughout our evolution, our survival depended on making reasonably accurate risk management decisions intuitively, and we’re so good at it, we don’t even realise we’re doing it.

Parents know this. Children have surprisingly perceptive risk intuition. They know when parents are serious about a threat and when their threats are empty. And they respond to the real risks of parental punishment, not the inflated risks based on parental rhetoric. Again, awareness training lectures don’t work; there have to be real consequences.

It gets even weirder. The University College London professor John Adams popularised the metaphor of a mental risk thermostat. We tend to seek some natural level of risk, and if something becomes less risky, we tend to make it more risky. Motorcycle riders who wear helmets drive faster than riders who don’t.

Our risk thermostats aren’t perfect (that newly helmeted motorcycle rider will still decrease his overall risk) and will tend to remain within the same domain (he might drive faster, but he won’t increase his risk by taking up smoking), but in general, people demonstrate an innate and finely tuned ability to understand and respond to risks.

Of course, our risk intuition fails spectacularly and often, with regards to rare risks , unknown risks, voluntary risks, and so on. But when it comes to the common risks we face every day—the kinds of risks our evolutionary survival depended on—we’re pretty good.

So whenever you see someone in a situation who you think doesn’t understand the risks, stop first and make sure you understand the risks. You might be surprised.

This essay previously appeared in The Guardian.

EDITED TO ADD (8/12): Commentary on risk thermostat.

Posted on August 6, 2009 at 5:08 AM • View Comments

Building in Surveillance

China is the world’s most successful Internet censor. While the Great Firewall of China isn’t perfect, it effectively limits information flowing in and out of the country. But now the Chinese government is taking things one step further.

Under a requirement taking effect soon, every computer sold in China will have to contain the Green Dam Youth Escort software package. Ostensibly a pornography filter, it is government spyware that will watch every citizen on the Internet.

Green Dam has many uses. It can police a list of forbidden Web sites. It can monitor a user’s reading habits. It can even enlist the computer in some massive botnet attack, as part of a hypothetical future cyberwar.

China’s actions may be extreme, but they’re not unique. Democratic governments around the world—Sweden, Canada and the United Kingdom, for example—are rushing to pass laws giving their police new powers of Internet surveillance, in many cases requiring communications system providers to redesign products and services they sell.

Many are passing data retention laws, forcing companies to keep information on their customers. Just recently, the German government proposed giving itself the power to censor the Internet.

The United States is no exception. The 1994 CALEA law required phone companies to facilitate FBI eavesdropping, and since 2001, the NSA has built substantial eavesdropping systems in the United States. The government has repeatedly proposed Internet data retention laws, allowing surveillance into past activities as well as present.

Systems like this invite criminal appropriation and government abuse. New police powers, enacted to fight terrorism, are already used in situations of normal crime. Internet surveillance and control will be no different.

Official misuses are bad enough, but the unofficial uses worry me more. Any surveillance and control system must itself be secured. An infrastructure conducive to surveillance and control invites surveillance and control, both by the people you expect and by the people you don’t.

China’s government designed Green Dam for its own use, but it’s been subverted. Why does anyone think that criminals won’t be able to use it to steal bank account and credit card information, use it to launch other attacks, or turn it into a massive spam-sending botnet?

Why does anyone think that only authorized law enforcement will mine collected Internet data or eavesdrop on phone and IM conversations?

These risks are not theoretical. After 9/11, the National Security Agency built a surveillance infrastructure to eavesdrop on telephone calls and e-mails within the United States.

Although procedural rules stated that only non-Americans and international phone calls were to be listened to, actual practice didn’t always match those rules. NSA analysts collected more data than they were authorized to, and used the system to spy on wives, girlfriends, and famous people such as President Clinton.

But that’s not the most serious misuse of a telecommunications surveillance infrastructure. In Greece, between June 2004 and March 2005, someone wiretapped more than 100 cell phones belonging to members of the Greek government—the prime minister and the ministers of defense, foreign affairs and justice.

Ericsson built this wiretapping capability into Vodafone’s products, and enabled it only for governments that requested it. Greece wasn’t one of those governments, but someone still unknown—a rival political party? organized crime?—figured out how to surreptitiously turn the feature on.

Researchers have already found security flaws in Green Dam that would allow hackers to take over the computers. Of course there are additional flaws, and criminals are looking for them.

Surveillance infrastructure can be exported, which also aids totalitarianism around the world. Western companies like Siemens, Nokia, and Secure Computing built Iran’s surveillance infrastructure. U.S. companies helped build China’s electronic police state. Twitter’s anonymity saved the lives of Iranian dissidents—anonymity that many governments want to eliminate.

Every year brings more Internet censorship and control—not just in countries like China and Iran, but in the United States, the United Kingdom, Canada and other free countries.

The control movement is egged on by both law enforcement, trying to catch terrorists, child pornographers and other criminals, and by media companies, trying to stop file sharers.

It’s bad civic hygiene to build technologies that could someday be used to facilitate a police state. No matter what the eavesdroppers and censors say, these systems put us all at greater risk. Communications systems that have no inherent eavesdropping capabilities are more secure than systems with those capabilities built in.

This essay previously appeared—albeit with fewer links—on the Minnesota Public Radio website.

Posted on August 3, 2009 at 6:43 AM • View Comments

Privacy Salience and Social Networking Sites

Reassuring people about privacy makes them more, not less, concerned. It’s called “privacy salience,” and Leslie John, Alessandro Acquisti, and George Loewenstein—all at Carnegie Mellon University—demonstrated this in a series of clever experiments. In one, subjects completed an online survey consisting of a series of questions about their academic behavior—”Have you ever cheated on an exam?” for example. Half of the subjects were first required to sign a consent warning—designed to make privacy concerns more salient—while the other half did not. Also, subjects were randomly assigned to receive either a privacy confidentiality assurance, or no such assurance. When the privacy concern was made salient (through the consent warning), people reacted negatively to the subsequent confidentiality assurance and were less likely to reveal personal information.

In another experiment, subjects completed an online survey where they were asked a series of personal questions, such as “Have you ever tried cocaine?” Half of the subjects completed a frivolous-looking survey—”How BAD are U??”—with a picture of a cute devil. The other half completed the same survey with the title “Carnegie Mellon University Survey of Ethical Standards,” complete with a university seal and official privacy assurances. The results showed that people who were reminded about privacy were less likely to reveal personal information than those who were not.

Privacy salience does a lot to explain social networking sites and their attitudes towards privacy. From a business perspective, social networking sites don’t want their members to exercise their privacy rights very much. They want members to be comfortable disclosing a lot of data about themselves.

Joseph Bonneau and Soeren Preibusch of Cambridge University have been studying privacy on 45 popular social networking sites around the world. (You may not have realized that there are 45 popular social networking sites around the world.) They found that privacy settings were often confusing and hard to access; Facebook, with its 61 privacy settings, is the worst. To understand some of the settings, they had to create accounts with different settings so they could compare the results. Privacy tends to increase with the age and popularity of a site. General-use sites tend to have more privacy features than niche sites.

But their most interesting finding was that sites consistently hide any mentions of privacy. Their splash pages talk about connecting with friends, meeting new people, sharing pictures: the benefits of disclosing personal data.

These sites do talk about privacy, but only on hard-to-find privacy policy pages. There, the sites give strong reassurances about their privacy controls and the safety of data members choose to disclose on the site. There, the sites display third-party privacy seals and other icons designed to assuage any fears members have.

It’s the Carnegie Mellon experimental result in the real world. Users care about privacy, but don’t really think about it day to day. The social networking sites don’t want to remind users about privacy, even if they talk about it positively, because any reminder will result in users remembering their privacy fears and becoming more cautious about sharing personal data. But the sites also need to reassure those “privacy fundamentalists” for whom privacy is always salient, so they have very strong pro-privacy rhetoric for those who take the time to search them out. The two different marketing messages are for two different audiences.

Social networking sites are improving their privacy controls as a result of public pressure. At the same time, there is a counterbalancing business pressure to decrease privacy; watch what’s going on right now on Facebook, for example. Naively, we should expect companies to make their privacy policies clear to allow customers to make an informed choice. But the marketing need to reduce privacy salience will frustrate market solutions to improve privacy; sites would much rather obfuscate the issue than compete on it as a feature.

This essay originally appeared in the Guardian.

Posted on July 16, 2009 at 6:05 AM • View Comments

North Korean Cyberattacks

To hear the media tell it, the United States suffered a major cyberattack last week. Stories were everywhere. "Cyber Blitz hits U.S., Korea" was the headline in Thursday’s Wall Street Journal. North Korea was blamed.

Where were you when North Korea attacked America? Did you feel the fury of North Korea’s armies? Were you fearful for your country? Or did your resolve strengthen, knowing that we would defend our homeland bravely and valiantly?

My guess is that you didn’t even notice, that—if you didn’t open a newspaper or read a news website—you had no idea anything was happening. Sure, a few government websites were knocked out, but that’s not alarming or even uncommon. Other government websites were attacked but defended themselves, the sort of thing that happens all the time. If this is what an international cyberattack looks like, it hardly seems worth worrying about at all.

Politically motivated cyber attacks are nothing new. We’ve seen UK vs. Ireland. Israel vs. the Arab states. Russia vs. several former Soviet Republics. India vs. Pakistan, especially after the nuclear bomb tests in 1998. China vs. the United States, especially in 2001 when a U.S. spy plane collided with a Chinese fighter jet. And so on and so on.

The big one happened in 2007, when the government of Estonia was attacked in cyberspace following a diplomatic incident with Russia about the relocation of a Soviet World War II memorial. The networks of many Estonian organizations, including the Estonian parliament, banks, ministries, newspapers and broadcasters, were attacked and—in many cases—shut down. Estonia was quick to blame Russia, which was equally quick to deny any involvement.

It was hyped as the first cyberwar, but after two years there is still no evidence that the Russian government was involved. Though Russian hackers were indisputably the major instigators of the attack, the only individuals positively identified have been young ethnic Russians living inside Estonia, who were angry over the statue incident.

Poke at any of these international incidents, and what you find are kids playing politics. Last Wednesday, South Korea’s National Intelligence Service admitted that it didn’t actually know that North Korea was behind the attacks: "North Korea or North Korean sympathizers in the South" was what it said. Once again, it’ll be kids playing politics.

This isn’t to say that cyberattacks by governments aren’t an issue, or that cyberwar is something to be ignored. The constant attacks by Chinese nationals against U.S. networks may not be government-sponsored, but it’s pretty clear that they’re tacitly government-approved. Criminals, from lone hackers to organized crime syndicates, attack networks all the time. And war expands to fill every possible theater: land, sea, air, space, and now cyberspace. But cyberterrorism is nothing more than a media invention designed to scare people. And for there to be a cyberwar, there first needs to be a war.

Israel is currently considering attacking Iran in cyberspace, for example. If it tries, it’ll discover that attacking computer networks is an inconvenience to the nuclear facilities it’s targeting, but doesn’t begin to substitute for bombing them.

In May, President Obama gave a major speech on cybersecurity. He was right when he said that cybersecurity is a national security issue, and that the government needs to step up and do more to prevent cyberattacks. But he couldn’t resist hyping the threat with scare stories: "In one of the most serious cyber incidents to date against our military networks, several thousand computers were infected last year by malicious software—malware," he said. What he didn’t add was that those infections occurred because the Air Force couldn’t be bothered to keep its patches up to date.

This is the face of cyberwar: easily preventable attacks that, even when they succeed, only a few people notice. Even this current incident is turning out to be a sloppily modified five-year-old worm that no modern network should still be vulnerable to.

Securing our networks doesn’t require some secret advanced NSA technology. It’s the boring network security administration stuff we already know how to do: keep your patches up to date, install good anti-malware software, correctly configure your firewalls and intrusion-detection systems, monitor your networks. And while some government and corporate networks do a pretty good job at this, others fail again and again.

Enough of the hype and the bluster. The news isn’t the attacks, but that some networks had security lousy enough to be vulnerable to them.

This essay originally appeared on the Minnesota Public Radio website.

Posted on July 13, 2009 at 11:45 AM • View Comments

Security, Group Size, and the Human Brain

If the size of your company grows past 150 people, it’s time to get name badges. It’s not that larger groups are somehow less secure, it’s just that 150 is the cognitive limit to the number of people a human brain can maintain a coherent social relationship with.

Primatologist Robin Dunbar derived this number by comparing neocortex—the “thinking” part of the mammalian brain—volume with the size of primate social groups. By analyzing data from 38 primate genera and extrapolating to the human neocortex size, he predicted a human “mean group size” of roughly 150.

This number appears regularly in human society; it’s the estimated size of a Neolithic farming village, the size at which Hittite settlements split, and the basic unit in professional armies from Roman times to the present day. Larger group sizes aren’t as stable because their members don’t know each other well enough. Instead of thinking of the members as people, we think of them as groups of people. For such groups to function well, they need externally imposed structure, such as name badges.

Of course, badges aren’t the only way to determine in-group/out-group status. Other markers include insignia, uniforms, and secret handshakes. They have different security properties and some make more sense than others at different levels of technology, but once a group reaches 150 people, it has to do something.

More generally, there are several layers of natural human group size that increase with a ratio of approximately three: 5, 15, 50, 150, 500, and 1500—although, really, the numbers aren’t as precise as all that, and groups that are less focused on survival tend to be smaller. The layers relate to both the intensity and intimacy of relationship and the frequency of contact.

The smallest, three to five, is a “clique”: the number of people from whom you would seek help in times of severe emotional distress. The twelve to 20 group is the “sympathy group”: people with which you have special ties. After that, 30 to 50 is the typical size of hunter-gatherer overnight camps, generally drawn from the same pool of 150 people. No matter what size company you work for, there are only about 150 people you consider to be “co-workers.” (In small companies, Alice and Bob handle accounting. In larger companies, it’s the accounting department—and maybe you know someone there personally.) The 500-person group is the “megaband,” and the 1,500-person group is the “tribe.” Fifteen hundred is roughly the number of faces we can put names to, and the typical size of a hunter-gatherer society.

These numbers are reflected in military organization throughout history: squads of 10 to 15 organized into platoons of three to four squads, organized into companies of three to four platoons, organized into battalions of three to four companies, organized into regiments of three to four battalions, organized into divisions of two to three regiments, and organized into corps of two to three divisions.

Coherence can become a real problem once organizations get above about 150 in size. So as group sizes grow across these boundaries, they have more externally imposed infrastructure—and more formalized security systems. In intimate groups, pretty much all security is ad hoc. Companies smaller than 150 don’t bother with name badges; companies greater than 500 hire a guard to sit in the lobby and check badges. The military have had centuries of experience with this under rather trying circumstances, but even there the real commitment and bonding invariably occurs at the company level. Above that you need to have rank imposed by discipline.

The whole brain-size comparison might be bunk, and a lot of evolutionary psychologists disagree with it. But certainly security systems become more formalized as groups grow larger and their members less known to each other. When do more formal dispute resolution systems arise: town elders, magistrates, judges? At what size boundary are formal authentication schemes required? Small companies can get by without the internal forms, memos, and procedures that large companies require; when does what tend to appear? How does punishment formalize as group size increase? And how do all these things affect group coherence? People act differently on social networking sites like Facebook when their list of “friends” grows larger and less intimate. Local merchants sometimes let known regulars run up tabs. I lend books to friends with much less formality than a public library. What examples have you seen?

An edited version of this essay, without links, appeared in the July/August 2009 issue of IEEE Security & Privacy.

Posted on July 1, 2009 at 6:51 AM • View Comments

Authenticating Paperwork

It’s a sad, horrific story. Homeowner returns to find his house demolished. The demolition company was hired legitimately but there was a mistake and it demolished the wrong house. The demolition company relied on GPS co-ordinates, but requiring street addresses isn’t a solution. A typo in the address is just as likely, and it would have demolished the house just as quickly.

The problem is less how the demolishers knew which house to knock down, and more how they confirmed that knowledge. They trusted the paperwork, and the paperwork was wrong. Informality works when everybody knows everybody else. When merchants and customers know each other, government officials and citizens know each other, and people know their neighbours, people know what’s going on. In that sort of milieu, if something goes wrong, people notice.

In our modern anonymous world, paperwork is how things get done. Traditionally, signatures, forms, and watermarks all made paperwork official. Forgeries were possible but difficult. Today, there’s still paperwork, but for the most part it only exists until the information makes its way into a computer database. Meanwhile, modern technology—computers, fax machines and desktop publishing software—has made it easy to forge paperwork. Every case of identity theft has, at its core, a paperwork failure. Fake work orders, purchase orders, and other documents are used to steal computers, equipment, and stock. Occasionally, fake faxes result in people being sprung from prison. Fake boarding passes can get you through airport security. This month hackers officially changed the name of a Swedish man.

A reporter even changed the ownership of the Empire State Building. Sure, it was a stunt, but this is a growing form of crime. Someone pretends to be you—preferably when you’re away on holiday—and sells your home to someone else, forging your name on the paperwork. You return to find someone else living in your house, someone who thinks he legitimately bought it. In some senses, this isn’t new. Paperwork mistakes and fraud have happened ever since there was paperwork. And the problem hasn’t been fixed yet for several reasons.

One, our sloppy systems generally work fine, and it’s how we get things done with minimum hassle. Most people’s houses don’t get demolished and most people’s names don’t get maliciously changed. As common as identity theft is, it doesn’t happen to most of us. These stories are news because they are so rare. And in many cases, it’s cheaper to pay for the occasional blunder than ensure it never happens.

Two, sometimes the incentives aren’t in place for paperwork to be properly authenticated. The people who demolished that family home were just trying to get a job done. The same is true for government officials processing title and name changes. Banks get paid when money is transferred from one account to another, not when they find a paperwork problem. We’re all irritated by forms stamped 17 times, and other mysterious bureaucratic processes, but these are actually designed to detect problems.

And three, there’s a psychological mismatch: it is easy to fake paperwork, yet for the most part we act as if it has magical properties of authenticity.

What’s changed is scale. Fraud can be perpetrated against hundreds of thousands, automatically. Mistakes can affect that many people, too. What we need are laws that penalise people or companies—criminally or civilly—who make paperwork errors. This raises the cost of mistakes, making authenticating paperwork more attractive, which changes the incentives of those on the receiving end of the paperwork. And that will cause the market to devise technologies to verify the provenance, accuracy, and integrity of information: telephone verification, addresses and GPS co-ordinates, cryptographic authentication, systems that double- and triple-check, and so on.

We can’t reduce society’s reliance on paperwork, and we can’t eliminate errors based on it. But we can put economic incentives in place for people and companies to authenticate paperwork more.

This essay originally appeared in The Guardian.

Posted on June 25, 2009 at 6:11 AM • View Comments

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Sidebar photo of Bruce Schneier by Joe MacInnis.