Entries Tagged "malware"

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Updating the Traditional Security Model

On the Firewall Wizards mailing list last year, Dave Piscitello made a fascinating observation. Commenting on the traditional four-step security model:

Authentication (who are you)
Authorization (what are you allowed to do)
Availability (is the data accessible)
Authenticity (is the data intact)

Piscitello said:

This model is no longer sufficient because it does not include asserting the trustworthiness of the endpoint device from which a (remote) user will authenticate and subsequently access data. Network admission and endpoint control are needed to determine that the device is free of malware (esp. key loggers) before you even accept a keystroke from a user. So let’s prepend “admissibility” to your list, and come up with a 5-legged stool, or call it the Pentagon of Trust.

He’s 100% right.

Posted on August 1, 2006 at 2:03 PM • View Comments

Bot Networks

What could you do if you controlled a network of thousands of computers—or, at least, could use the spare processor cycles on those machines? You could perform massively parallel computations: model nuclear explosions or global weather patterns, factor large numbers or find Mersenne primes, or break cryptographic problems.

All of these are legitimate applications. And you can visit distributed.net and download software that allows you to donate your spare computer cycles to some of these projects. (You can help search for Optimal Golomb Rulers—even if you have no idea what they are.) You’ve got a lot of cycles to spare. There’s no reason that your computer can’t help search for extraterrestrial life as it, for example, sits idly waiting for you to read this essay.

The reason these things work is that they are consensual; none of these projects download software onto your computer without your knowledge. None of these projects control your computer without your consent. But there are lots of software programs that do just that.

The term used for a computer remotely controlled by someone else is a “bot”. A group of computers—thousands or even millions—controlled by someone else is a bot network. Estimates are that millions of computers on the internet today are part of bot networks, and the largest bot networks have over 1.5 million machines.

Initially, bot networks were used for just one thing: denial-of-service attacks. Hackers would use them against each other, fighting hacker feuds in cyberspace by attacking each other’s computers. The first widely publicized use of a distributed intruder tool—technically not a botnet, but practically the same thing—was in February 2000, when Canadian hacker Mafiaboy directed an army of compromised computers to flood CNN.com, Amazon.com, eBay, Dell Computer and other sites with debilitating volumes of traffic. Every newspaper carried that story.

These days, bot networks are more likely to be controlled by criminals than by hackers. The important difference is the motive: profit. Networks are being used to send phishing e-mails and other spam. They’re being used for click fraud. They’re being used as an extortion tool: Pay up or we’ll DDoS you!

Mostly, they’re being used to collect personal data for fraud—commonly called “identity theft.” Modern bot software doesn’t just attack other computers; it attacks its hosts as well. The malware is packed with keystroke loggers to steal passwords and account numbers. In fact, many bots automatically hunt for financial information, and some botnets have been built solely for this purpose—to gather credit card numbers, online banking passwords, PayPal accounts, and so on, from compromised hosts.

Swindlers are also using bot networks for click fraud. Google’s anti-fraud systems are sophisticated enough to detect thousands of clicks by one computer; it’s much harder to determine if a single click by each of thousands of computers is fraud, or just popularity.

And, of course, most bots constantly search for other computers that can be infected and added to the bot network. (A 1.5 million-node bot network was discovered in the Netherlands last year. The command-and-control system was dismantled, but some of the bots are still active, infecting other computers and adding them to this defunct network.)

Modern bot networks are remotely upgradeable, so the operators can add new functionality to the bots at any time, or switch from one bot program to another. Bot authors regularly upgrade their botnets during development, or to evade detection by anti-virus and malware cleanup tools.

One application of bot networks that we haven’t seen all that much of is to launch a fast-spreading worm. (Some believe the Witty worm spread this way.) Much has been written about “flash worms” that can saturate the internet in 15 minutes or less. The situation gets even worse if 10 thousand bots synchronize their watches and release the worm at exactly the same time. Why haven’t we seen more of this? My guess is because there isn’t any profit in it.

There’s no real solution to the botnet problem, because there’s no single problem. There are many different bot networks, controlled in many different ways, consisting of computers infected through many different vulnerabilities. Really, a bot network is nothing more than an attacker taking advantage of 1) one or more software vulnerabilities, and 2) the economies of scale that computer networks bring. It’s the same thing as distributed.net or SETI@home, only the attacker doesn’t ask your permission first.

As long as networked computers have vulnerabilities—and that’ll be for the foreseeable future—there’ll be bot networks. It’s a natural side-effect of a computer network with bugs.

This essay originally appeared on Wired.com.

EDITED TO ADD (7/27): DDOS extortion is a bigger problem than you might think. Right now it’s primarily targeted against fringe industries—online gaming, online gambling, online porn—located offshore, but we’re seeing more and more of against mainstream companies in the U.S. and Europe.

EDITED TO ADD (7/27): Seems that Witty was definitely not seeded from a bot network.

Posted on July 27, 2006 at 6:35 AM • View Comments

Hacked MySpace Server Infects a Million Computers with Malware

According to The Washington Post:

An online banner advertisement that ran on MySpace.com and other sites over the past week used a Windows security flaw to infect more than a million users with spyware when people merely browsed the sites with unpatched versions of Windows….

Clever attack.

EDITED TO ADD (7/27): It wasn’t MySpace that was hacked, but a server belonging to the third-party advertising service that MySpace uses. The ad probably appeared on other websites as well, but MySpace seems to have been the biggest one.

EDITED TO ADD (8/5): Ed Felten comments.

Posted on July 24, 2006 at 6:46 AM • View Comments

Click Fraud and the Problem of Authenticating People

Google’s $6 billion-a-year advertising business is at risk because it can’t be sure that anyone is looking at its ads. The problem is called click fraud, and it comes in two basic flavors.

With network click fraud, you host Google AdSense advertisements on your own website. Google pays you every time someone clicks on its ad on your site. It’s fraud if you sit at the computer and repeatedly click on the ad or—better yet—write a computer program that repeatedly clicks on the ad. That kind of fraud is easy for Google to spot, so the clever network click fraudsters simulate different IP addresses, or install Trojan horses on other people’s computers to generate the fake clicks.

The other kind of click fraud is competitive. You notice your business competitor has bought an ad on Google, paying Google for each click. So you use the above techniques to repeatedly click on his ads, forcing him to spend money—sometimes a lot of money—on nothing. (Here’s a company that will commit click fraud for you.)

Click fraud has become a classic security arms race. Google improves its fraud-detection tools, so the fraudsters get increasingly clever … and the cycle continues. Meanwhile, Google is facing multiple lawsuits from those who claim the company isn’t doing enough. My guess is that everyone is right: It’s in Google’s interest both to solve and to downplay the importance of the problem.

But the overarching problem is both hard to solve and important: How do you tell if there’s an actual person sitting in front of a computer screen? How do you tell that the person is paying attention, hasn’t automated his responses, and isn’t being assisted by friends? Authentication systems are big business, whether based on something you know (passwords), something you have (tokens) or something you are (biometrics). But none of those systems can secure you against someone who walks away and lets another person sit down at the keyboard, or a computer that’s infected with a Trojan.

This problem manifests itself in other areas as well.

For years, online computer game companies have been battling players who use computer programs to assist their play: programs that allow them to shoot perfectly or see information they normally couldn’t see.

Playing is less fun if everyone else is computer-assisted, but unless there’s a cash prize on the line, the stakes are small. Not so with online poker sites, where computer-assisted players—or even computers playing without a real person at all—have the potential to drive all the human players away from the game.

Look around the internet, and you see this problem pop up again and again. The whole point of CAPTCHAs is to ensure that it’s a real person visiting a website, not just a bot on a computer. Standard testing doesn’t work online, because the tester can’t be sure that the test taker doesn’t have his book open, or a friend standing over his shoulder helping him. The solution in both cases is a proctor, of course, but that’s not always practical and obviates the benefits of internet testing.

This problem has even come up in court cases. In one instance, the prosecution demonstrated that the defendant’s computer committed some hacking offense, but the defense argued that it wasn’t the defendant who did it—that someone else was controlling his computer. And in another case, a defendant charged with a child porn offense argued that, while it was true that illegal material was on his computer, his computer was in a common room of his house and he hosted a lot of parties—and it wasn’t him who’d downloaded the porn.

Years ago, talking about security, I complained about the link between computer and chair. The easy part is securing digital information: on the desktop computer, in transit from computer to computer or on massive servers. The hard part is securing information from the computer to the person. Likewise, authenticating a computer is much easier than authenticating a person sitting in front of the computer. And verifying the integrity of data is much easier than verifying the integrity of the person looking at it—in both senses of that word.

And it’s a problem that will get worse as computers get better at imitating people.

Google is testing a new advertising model to deal with click fraud: cost-per-action ads. Advertisers don’t pay unless the customer performs a certain action: buys a product, fills out a survey, whatever. It’s a hard model to make work—Google would become more of a partner in the final sale instead of an indifferent displayer of advertising—but it’s the right security response to click fraud: Change the rules of the game so that click fraud doesn’t matter.

That’s how to solve a security problem.

This essay appeared on Wired.com.

EDITED TO ADD (7/13): Click Monkeys is a hoax site.

EDITED TO ADD (7/25): An evalution of Google’s anti-click-fraud efforts, as part of the Lane Gifts case. I’m not sure if this expert report was done for Google, for Lane Gifts, or for the judge.

Posted on July 13, 2006 at 5:22 AM • View Comments

Hacking Computers Over USB

I’ve previously written about the risks of small portable computing devices; how more and more data can be stored on them, and then lost or stolen. But there’s another risk: if an attacker can convince you to plug his USB device into your computer, he can take it over.

Plug an iPod or USB stick into a PC running Windows and the device can literally take over the machine and search for confidential documents, copy them back to the iPod or USB’s internal storage, and hide them as “deleted” files. Alternatively, the device can simply plant spyware, or even compromise the operating system. Two features that make this possible are the Windows AutoRun facility and the ability of peripherals to use something called direct memory access (DMA). The first attack vector you can and should plug; the second vector is the result of a design flaw that’s likely to be with us for many years to come.

The article has the details, but basically you can configure a file on your USB device to automatically run when it’s plugged into a computer. That file can, of course, do anything you want it to.

Recently I’ve been seeing more and more written about this attack. The Spring 2006 issue of 2600 Magazine, for example, contains a short article called “iPod Sneakiness” (unfortunately, not on line). The author suggests that you can innocently ask someone at an Internet cafe if you can plug your iPod into his computer to power it up—and then steal his passwords and critical files.

And here’s an article about someone who used this trick in a penetration test:

We figured we would try something different by baiting the same employees that were on high alert. We gathered all the worthless vendor giveaway thumb drives collected over the years and imprinted them with our own special piece of software. I had one of my guys write a Trojan that, when run, would collect passwords, logins and machine-specific information from the user’s computer, and then email the findings back to us.

The next hurdle we had was getting the USB drives in the hands of the credit union’s internal users. I made my way to the credit union at about 6 a.m. to make sure no employees saw us. I then proceeded to scatter the drives in the parking lot, smoking areas, and other areas employees frequented.

Once I seeded the USB drives, I decided to grab some coffee and watch the employees show up for work. Surveillance of the facility was worth the time involved. It was really amusing to watch the reaction of the employees who found a USB drive. You know they plugged them into their computers the minute they got to their desks.

I immediately called my guy that wrote the Trojan and asked if anything was received at his end. Slowly but surely info was being mailed back to him. I would have loved to be on the inside of the building watching as people started plugging the USB drives in, scouring through the planted image files, then unknowingly running our piece of software.

There is a defense. From the first article:

AutoRun is just a bad idea. People putting CD-ROMs or USB drives into their computers usually want to see what’s on the media, not have programs automatically run. Fortunately you can turn AutoRun off. A simple manual approach is to hold down the “Shift” key when a disk or USB storage device is inserted into the computer. A better way is to disable the feature entirely by editing the Windows Registry. There are many instructions for doing this online (just search for “disable autorun”) or you can download and use Microsoft’s TweakUI program, which is part of the Windows XP PowerToys download. With Windows XP you can also disable AutoRun for CDs by right-clicking on the CD drive icon in the Windows explorer, choosing the AutoPlay tab, and then selecting “Take no action” for each kind of disk that’s listed. Unfortunately, disabling AutoPlay for CDs won’t always disable AutoPlay for USB devices, so the registry hack is the safest course of action.

In the 1990s, the Macintosh operating system had this feature, which was removed after a virus made use of it in 1998. Microsoft needs to remove this feature as well.

EDITED TO ADD (6/12): In the penetration test, they didn’t use AutoRun.

Posted on June 8, 2006 at 1:34 PM • View Comments

Spammers Win One

Blue Security was an Israeli company that fought spam with spam:

Eran Reshef had an idea in the battle against spam e-mail that seemed to be working: he fought spam with spam. Today, he’ll give up the fight.

Reshef’s Silicon Valley company, Blue Security Inc., simply asked the spammers to stop sending junk e-mail to his clients. But because those sort of requests tend to be ignored, Blue Security took them to a new level: it bombarded the spammers with requests from all 522,000 of its customers at the same time.

That led to a flood of Internet traffic so heavy that it disrupted the spammers’ ability to send e-mails to other victims—a crippling effect that caused a handful of known spammers to comply with the requests.

Then, earlier this month, a Russia-based spammer counterattacked, Reshef said. Using tens of thousands of hijacked computers, the spammer flooded Blue Security with so much Internet traffic that it blocked legitimate visitors from going to Bluesecurity.com, as well as to other Web sites. The spammer also sent another message: Cease operations or Blue Security customers will soon find themselves targeted with virus-filled attacks.

Last week Blue Security gave up:

Wednesday, Blue Security said it had to give up because it couldn’t sustain the fight against spammers. “Several leading spammers viewed [us] as a strategic threat to their spam business,” Eran Reshef, Blue Security chief executive wrote in the message posted to the company’s site.

“After recovering from the attack, we determined that once we reactivated the Blue Community, spammers would resume their attacks. We cannot take the responsibility for an ever-escalating cyber war through our continued operations.

“As much as it saddens us, we believe this is the responsible thing to do,” said Reshef, who did not respond to an e-mail requesting additional comment. Later Wednesday, a spokesman said that the company would not be making any additional statements beyond the message on its site.

Another news article. And Marcus Ranum on Blue Security’s idea.

Posted on May 23, 2006 at 12:58 PM • View Comments

Who Owns Your Computer?

When technology serves its owners, it is liberating. When it is designed to serve others, over the owner’s objection, it is oppressive. There’s a battle raging on your computer right now—one that pits you against worms and viruses, Trojans, spyware, automatic update features and digital rights management technologies. It’s the battle to determine who owns your computer.

You own your computer, of course. You bought it. You paid for it. But how much control do you really have over what happens on your machine? Technically you might have bought the hardware and software, but you have less control over what it’s doing behind the scenes.

Using the hacker sense of the term, your computer is “owned” by other people.

It used to be that only malicious hackers were trying to own your computers. Whether through worms, viruses, Trojans or other means, they would try to install some kind of remote-control program onto your system. Then they’d use your computers to sniff passwords, make fraudulent bank transactions, send spam, initiate phishing attacks and so on. Estimates are that somewhere between hundreds of thousands and millions of computers are members of remotely controlled “bot” networks. Owned.

Now, things are not so simple. There are all sorts of interests vying for control of your computer. There are media companies that want to control what you can do with the music and videos they sell you. There are companies that use software as a conduit to collect marketing information, deliver advertising or do whatever it is their real owners require. And there are software companies that are trying to make money by pleasing not only their customers, but other companies they ally themselves with. All these companies want to own your computer.

Some examples:

  • Entertainment software: In October 2005, it emerged that Sony had distributed a rootkit with several music CDs—the same kind of software that crackers use to own people’s computers. This rootkit secretly installed itself when the music CD was played on a computer. Its purpose was to prevent people from doing things with the music that Sony didn’t approve of: It was a DRM system. If the exact same piece of software had been installed secretly by a hacker, this would have been an illegal act. But Sony believed that it had legitimate reasons for wanting to own its customers’ machines.
  • Antivirus: You might have expected your antivirus software to detect Sony’s rootkit. After all, that’s why you bought it. But initially, the security programs sold by Symantec and others did not detect it, because Sony had asked them not to. You might have thought that the software you bought was working for you, but you would have been wrong.
  • Internet services: Hotmail allows you to blacklist certain e-mail addresses, so that mail from them automatically goes into your spam trap. Have you ever tried blocking all that incessant marketing e-mail from Microsoft? You can’t.
  • Application software: Internet Explorer users might have expected the program to incorporate easy-to-use cookie handling and pop-up blockers. After all, other browsers do, and users have found them useful in defending against Internet annoyances. But Microsoft isn’t just selling software to you; it sells Internet advertising as well. It isn’t in the company’s best interest to offer users features that would adversely affect its business partners.
  • Spyware: Spyware is nothing but someone else trying to own your computer. These programs eavesdrop on your behavior and report back to their real owners—sometimes without your knowledge or consent—about your behavior.
  • Internet security: It recently came out that the firewall in Microsoft Vista will ship with half its protections turned off. Microsoft claims that large enterprise users demanded this default configuration, but that makes no sense. It’s far more likely that Microsoft just doesn’t want adware—and DRM spyware—blocked by default.
  • Update: Automatic update features are another way software companies try to own your computer. While they can be useful for improving security, they also require you to trust your software vendor not to disable your computer for nonpayment, breach of contract or other presumed infractions.

Adware, software-as-a-service and Google Desktop search are all examples of some other company trying to own your computer. And Trusted Computing will only make the problem worse.

There is an inherent insecurity to technologies that try to own people’s computers: They allow individuals other than the computers’ legitimate owners to enforce policy on those machines. These systems invite attackers to assume the role of the third party and turn a user’s device against him.

Remember the Sony story: The most insecure feature in that DRM system was a cloaking mechanism that gave the rootkit control over whether you could see it executing or spot its files on your hard disk. By taking ownership away from you, it reduced your security.

If left to grow, these external control systems will fundamentally change your relationship with your computer. They will make your computer much less useful by letting corporations limit what you can do with it. They will make your computer much less reliable because you will no longer have control of what is running on your machine, what it does, and how the various software components interact. At the extreme, they will transform your computer into a glorified boob tube.

You can fight back against this trend by only using software that respects your boundaries. Boycott companies that don’t honestly serve their customers, that don’t disclose their alliances, that treat users like marketing assets. Use open-source software—software created and owned by users, with no hidden agendas, no secret alliances and no back-room marketing deals.

Just because computers were a liberating force in the past doesn’t mean they will be in the future. There is enormous political and economic power behind the idea that you shouldn’t truly own your computer or your software, despite having paid for it.

This essay originally appeared on Wired.com.

EDITED TO ADD (5/5): Commentary. It seems that some of my examples were not very good. I’ll come up with other ones for the Crypto-Gram version.

Posted on May 4, 2006 at 7:13 AM • View Comments

New Directions in Malware

Kaspersky Labs reports on extortion scams using malware:

We’ve reported more than once on cases where remote malicious users have moved away from the stealth use of infected computers (stealing data from them, using them as part of zombie networks etc) to direct blackmail, demanding payment from victims. At the moment, this method is used in two main ways: encrypting user data and corrupting system information.

Users quickly understand that something has happened to their data. They are then told that they should send a specific sum to an e-payment account maintained by the remote malicious user, whether it be EGold, Webmoney or whatever. The ransom demanded varies significantly depending on the amount of money available to the victim. We know of cases where the malicious users have demanded $50, and of cases where they have demanded more than $2,000. The first such blackmail case was in 1989, and now this method is again gaining in popularity.

In 2005, the most striking examples of this type of cybercrime were carried out using the Trojans GpCode and Krotten. The first of these encrypts user data; the second restricts itself to making a number of modifications to the victim machine’s system registry, causing it to cease functioning.

Among other worms, the article discusses the GpCode.ac worm, which encrypts data using 56-bit RSA (no, that’s not a typo). The whole article is interesting reading.

Posted on April 26, 2006 at 1:07 PM • View Comments

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Sidebar photo of Bruce Schneier by Joe MacInnis.