Entries Tagged "Conficker"

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Conficker

Conficker’s April Fool’s joke—the huge, menacing build-up and then nothing—is a good case study on how we think about risks, one whose lessons are applicable far outside computer security. Generally, our brains aren’t very good at probability and risk analysis. We tend to use cognitive shortcuts instead of thoughtful analysis. This worked fine for the simple risks we encountered for most of our species’s existence, but it’s less effective against the complex risks society forces us to face today.

We tend to judge the probability of something happening on how easily we can bring examples to mind. It’s why people tend to buy earthquake insurance after an earthquake, when the risk is lowest. It’s why those of us who have been the victims of a crime tend to fear crime more than those who haven’t. And it’s why we fear a repeat of 9/11 more than other types of terrorism.

We fear being murdered, kidnapped, raped and assaulted by strangers, when friends and relatives are far more likely to do those things to us. We worry about plane crashes instead of car crashes, which are far more common. We tend to exaggerate spectacular, strange, and rare events, and downplay more ordinary, familiar, and common ones.

We also respond more to stories than to data. If I show you statistics on crime in New York, you’ll probably shrug and continue your vacation planning. But if a close friend gets mugged there, you’re more likely to cancel your trip.

And specific stories are more convincing than general ones. That is why we buy more insurance against plane accidents than against travel accidents, or accidents in general. Or why, when surveyed, we are willing to pay more for air travel insurance covering “terrorist acts” than “all possible causes”. That is why, in experiments, people judge specific scenarios more likely than more general ones, even if the general ones include the specific.

Conficker’s 1 April deadline was precisely the sort of event humans tend to overreact to. It’s a specific threat, which convinces us that it’s credible. It’s a specific date, which focuses our fear. Our natural tendency to exaggerate makes it more spectacular, which further increases our fear. Its repetition by the media makes it even easier to bring to mind. As the story becomes more vivid, it becomes more convincing.

The New York Times called it an “unthinkable disaster”, the television news show 60 Minutes said it could “disrupt the entire internet” and we at the Guardian warned that it might be a “deadly threat”. Naysayers were few, and drowned out.

The first of April passed without incident, but Conficker is no less dangerous today. About 2.2m computers worldwide, are still infected with Conficker.A and B, and about 1.3m more are infected with the nastier Conficker.C. It’s true that on 1 April Conficker.C tried a new trick to update itself, but its authors could have updated the worm using another mechanism any day. In fact, they updated it on 8 April, and can do so again.

And Conficker is just one of many, many dangerous worms being run by criminal organisations. It came with a date and got a lot of press—that 1 April date was more hype than reality—but it’s not particularly special. In short, there are many criminal organisations on the internet using worms and other forms of malware to infect computers. They then use those computers to send spam, commit fraud, and infect more computers. The risks are real and serious. Luckily, keeping your anti-virus software up-to-date and not clicking on strange attachments can keep you pretty secure. Conficker spreads through a Windows vulnerability that was patched in October. You do have automatic update turned on, right?

But people being people, it takes a specific story for us to protect ourselves.

This essay previously appeared in The Guardian.

Posted on April 23, 2009 at 5:50 AM • View Comments

Another Conficker Variant

This is one well-designed piece of malware:

Conficker B++ is somewhat similar to Conficker B, with 294 of 297 sub-routines the same and 39 additional subroutines. The latest variant, first spotted on 16 February, is even more sneaky than its previous incarnations, SRI explains.

Conficker B++ is no longer limited to reinfection by similarly structured Conficker DLLs, but can now push new self-contained Win32 applications. These executables can infiltrate the host using methods that are not detected by the latest anti-Conficker security applications.

[…]

The malware also creates an additional backdoor on compromise machines to create an altogether trickier infectious agent, SRI explains.

In Conficker A and B, there appeared only one method to submit Win32 binaries to the digital signature validation path, and ultimately to the CreateProcess API call. This path required the use of the Internet rendezvous point to download the binary through an HTTP transaction.

Under Conficker B++, two new paths to binary validation and execution have been introduced to Conficker drones, both of which bypass the use of Internet Rendezvous points: an extension to the netapi32.dll patch and the new named pipe backdoor. These changes suggest a desire by the Conficker’s authors to move away from a reliance on Internet rendezvous points to support binary update, and toward a more direct flash approach.

SRI reckons that Conficker-A has infected 4.7m machines, at one time or another, while Conficker-B has hit 6.7m IP addresses. These figures, as with previous estimates, come from an analysis of the number of machines that have ever tried to call into malware update sites. The actual number of infected hosts at any one time is lower than that. SRI estimates the botnet controlled by Conficker-A and Conficker-B is around 1m and 3m hosts, respectively, or a third of the raw estimate.

Posted on February 24, 2009 at 5:23 AM • View Comments

Another Password Analysis

Here’s an analysis of 30,000 passwords from phpbb.com, similar to my analysis of 34,000 MySpace passwords:

The striking different between the two incidents is that the phpbb passwords are simpler. MySpace requires that passwords “must be between 6 and 10 characters, and contain at least 1 number or punctuation character.” Most people satisfied this requirement by simply appending “1” to the ends of their passwords. The phpbb site has no such restrictions—the passwords are shorter and rarely contain anything more than a dictionary word.

Seems like we still can’t choose good passwords. Conficker.B exploits this, trying about 200 common passwords to help spread itself.

Posted on February 20, 2009 at 7:31 AM • View Comments

Balancing Security and Usability in Authentication

Since January, the Conficker.B worm has been spreading like wildfire across the Internet: infecting the French Navy, hospitals in Sheffield, the court system in Houston, and millions of computers worldwide. One of the ways it spreads is by cracking administrator passwords on networks. Which leads to the important question: Why in the world are IT administrators still using easy-to-guess passwords?

Computer authentication systems have two basic requirements. They need to keep the bad guys from accessing your account, and they need to allow you to access your account. Both are important, and every authentication system is a balancing act between the two. Too little security, and the bad guys will get in too easily. But if the authentication system is too complicated, restrictive, or hard to use, you won’t be able to—or won’t bother to—use it.

Passwords are the most common authentication system, and a good place to start. They’re very easy to implement and use, which is why they’re so popular. But as computers have become faster, password guessing has become easier. Most people don’t choose passwords that are complicated enough to remain secure against modern password-guessing attacks. Conficker.B is even less clever; it just tries a list of about 200 common passwords.

To combat password guessing, many systems force users to choose harder-to-guess passwords—requiring minimum lengths, non alpha-numeric characters, etc.—and change their passwords more frequently. The first makes guessing harder, and the second makes a guessed password less valuable. This, of course, makes the system more annoying, so users respond by writing their passwords down and taping them to their monitors, or simply forgetting them more often. Smarter users write them down and put them in their wallets, or use a secure password database like Password Safe.

Users forgetting their passwords can be expensive—sysadmins or customer service reps have to field phone calls and reset passwords—so some systems include a backup authentication system: a secret question. The idea is that if you forget your password, you can authenticate yourself with some personal information that only you know. Your mother’s maiden name was traditional, but these days there are all sorts of secret questions: your favourite schoolteacher, favourite colour, street you grew up on, name of your first pet, and so on. This might make the system more usable, but it also makes it much less secure: answers can be easily guessable, and are often known by people close to you.

A common enhancement is a one-time password generator, like a SecurID token. This is a small device with a screen that displays a password that changes automatically once a minute. Adding this is called two-factor authentication, and is much more secure, because this token—”something you have”—is combined with a password—”something you know.” But it’s less usable, because the tokens have to be purchased and distributed to all users, and far too often it’s “something you lost or forgot.” And it costs money. Tokens are far more frequently used in corporate environments, but banks and some online gaming worlds have taken to using them—sometimes only as an option, because people don’t like them.

In most cases, how an authentication system works when a legitimate user tries to log on is much more important than how it works when an impostor tries to log on. No security system is perfect, and there is some level of fraud associated with any of these authentication methods. But the instances of fraud are rare compared to the number of times someone tries to log on legitimately. If a given authentication system let the bad guys in one in a hundred times, a bank could decide to live with the problem—or try to solve it in some other way. But if the same authentication system prevented legitimate customers from logging on even one in a thousand times, the number of complaints would be enormous and the system wouldn’t survive one week.

Balancing security and usability is hard, and many organizations get it wrong. But it’s also evolving; organizations needing to tighten their security continue to push more involved authentication methods, and more savvy Internet users are willing to accept them. And certainly IT administrators need to be leading that evolutionary change.

A version of this essay was originally published in The Guardian.

Posted on February 19, 2009 at 1:44 PM • View Comments

Sidebar photo of Bruce Schneier by Joe MacInnis.