Entries Tagged "malware"

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The Failure of Two-Factor Authentication

Two-factor authentication isn’t our savior. It won’t defend against phishing. It’s not going to prevent identity theft. It’s not going to secure online accounts from fraudulent transactions. It solves the security problems we had ten years ago, not the security problems we have today.

The problem with passwords is that they’re too easy to lose control of. People give them to other people. People write them down, and other people read them. People send them in e-mail, and that e-mail is intercepted. People use them to log into remote servers, and their communications are eavesdropped on. They’re also easy to guess. And once any of that happens, the password no longer works as an authentication token because you can’t be sure who is typing that password in.

Two-factor authentication mitigates this problem. If your password includes a number that changes every minute, or a unique reply to a random challenge, then it’s harder for someone else to intercept. You can’t write down the ever-changing part. An intercepted password won’t be good the next time it’s needed. And a two-factor password is harder to guess. Sure, someone can always give his password and token to his secretary, but no solution is foolproof.

These tokens have been around for at least two decades, but it’s only recently that they have gotten mass-market attention. AOL is rolling them out. Some banks are issuing them to customers, and even more are talking about doing it. It seems that corporations are finally waking up to the fact that passwords don’t provide adequate security, and are hoping that two-factor authentication will fix their problems.

Unfortunately, the nature of attacks has changed over those two decades. Back then, the threats were all passive: eavesdropping and offline password guessing. Today, the threats are more active: phishing and Trojan horses.

Here are two new active attacks we’re starting to see:

  • Man-in-the-Middle attack. An attacker puts up a fake bank website and entices user to that website. User types in his password, and the attacker in turn uses it to access the bank’s real website. Done right, the user will never realize that he isn’t at the bank’s website. Then the attacker either disconnects the user and makes any fraudulent transactions he wants, or passes along the user’s banking transactions while making his own transactions at the same time.

  • Trojan attack. Attacker gets Trojan installed on user’s computer. When user logs into his bank’s website, the attacker piggybacks on that session via the Trojan to make any fraudulent transaction he wants.

See how two-factor authentication doesn’t solve anything? In the first case, the attacker can pass the ever-changing part of the password to the bank along with the never-changing part. And in the second case, the attacker is relying on the user to log in.

The real threat is fraud due to impersonation, and the tactics of impersonation will change in response to the defenses. Two-factor authentication will force criminals to modify their tactics, that’s all.

Recently I’ve seen examples of two-factor authentication using two different communications paths: call it “two-channel authentication.” One bank sends a challenge to the user’s cell phone via SMS and expects a reply via SMS. If you assume that all your customers have cell phones, then this results in a two-factor authentication process without extra hardware. And even better, the second authentication piece goes over a different communications channel than the first; eavesdropping is much, much harder.

But in this new world of active attacks, no one cares. An attacker using a man-in-the-middle attack is happy to have the user deal with the SMS portion of the log-in, since he can’t do it himself. And a Trojan attacker doesn’t care, because he’s relying on the user to log in anyway.

Two-factor authentication is not useless. It works for local login, and it works within some corporate networks. But it won’t work for remote authentication over the Internet. I predict that banks and other financial institutions will spend millions outfitting their users with two-factor authentication tokens. Early adopters of this technology may very well experience a significant drop in fraud for a while as attackers move to easier targets, but in the end there will be a negligible drop in the amount of fraud and identity theft.

This essay will appear in the April issue of Communications of the ACM.

Posted on March 15, 2005 at 7:54 AMView Comments

Tracking Bot Networks

This is a fascinating piece of research on bot networks: networks of compromised computers that can be remotely controlled by an attacker. The paper details how bots and bot networks work, who uses them, how they are used, and how to track them.

From the conclusion:

In this paper we have attempted to demonstrate how honeynets can help us understand how botnets work, the threat they pose, and how attackers control them. Our research shows that some attackers are highly skilled and organized, potentially belonging to well organized crime structures. Leveraging the power of several thousand bots, it is viable to take down almost any website or network instantly. Even in unskilled hands, it should be obvious that botnets are a loaded and powerful weapon. Since botnets pose such a powerful threat, we need a variety of mechanisms to counter it.

Decentralized providers like Akamai can offer some redundancy here, but very large botnets can also pose a severe threat even against this redundancy. Taking down of Akamai would impact very large organizations and companies, a presumably high value target for certain organizations or individuals. We are currently not aware of any botnet usage to harm military or government institutions, but time will tell if this persists.

In the future, we hope to develop more advanced honeypots that help us to gather information about threats such as botnets. Examples include Client honeypots that actively participate in networks (e.g. by crawling the web, idling in IRC channels, or using P2P-networks) or modify honeypots so that they capture malware and send it to anti-virus vendors for further analysis. As threats continue to adapt and change, so must the security community.

Posted on March 14, 2005 at 10:46 AMView Comments

GhostBuster

This is a really interesting technical report from Microsoft. It describes a clever prototype — called GhostBuster — they developed for detecting arbitrary persistent and stealthy software, such as rootkits, Trojans, and software keyloggers. It’s a really elegant idea, based on a simple observation: the rootkit must exist on disk to be persistent, but must lie to programs running within the infected OS in order to hide.

Here’s how it works: The user has the GhostBuster program on a CD. He sticks the CD in the drive, and from within the (possibly corrupted) OS, the checker program runs: stopping all other user programs, flushing the caches, and then doing a complete checksum of all files on the disk and a scan of any registry keys that could autostart the system, writing out the results to a file on the hard drive.

Then the user is instructed to press the reset button, the CD boots its own OS, and the scan is repeated. Any differences indicate a rootkit or other stealth software, without the need for knowing what particular rootkits are or the proper checksums for the programs installed on disk.

Simple. Clever. Elegant.

In order to fool GhostBuster, the rootkit must 1) detect that such a checking program is running and either not lie to it or change the output as it’s written to disk (in the limit this becomes the halting problem for the rootkit designer), 2) integrate into the BIOS rather than the OS (tricky, platform specific, and not always possible), or 3) give up on either being persistent or stealthy. Thus this doesn’t eliminate rootkits entirely, but is a pretty mortal blow to persistent rootkits.

Of course, the concept could be adopted for any other operating system as well.

This is a great idea, but there’s a huge problem. GhostBuster is only a research prototype, so you can’t get a copy. And, even worse, Microsoft has no plans to turn it into a commercial tool.

This is too good an idea to abandon. Microsoft, if you’re listening, you should release this tool to the world. Make it public domain. Make it open source, even. It’s a great idea, and you deserve credit for coming up with it.

Any other security companies listening? Make and sell one of these. Anyone out there looking for an open source project? Here’s a really good one.

Note: I have no idea if Microsoft patented this idea. If they did and they don’t release it, shame on them. If they didn’t, good for them.

Posted on February 15, 2005 at 8:00 AMView Comments

Automobile Virus

SC Magazine is reporting on a virus that infects Lexus cars:

Lexus cars may be vulnerable to viruses that infect them via mobile phones. Landcruiser 100 models LX470 and LS430 have been discovered with infected operating systems that transfer within a range of 15 feet.

It seems that no one has done this yet, and the story is based on speculation that a cell phone can transfer a virus to the Lexus using Bluetooth. But it’s only a matter of time before something like this actually works.

Posted on February 2, 2005 at 8:00 AMView Comments

Clever Virus Attack

Just received this e-mail message, with an attachment entitled “schneier@counterpane.com.” The file is really an executable .com file, presumably one harboring a virus. Clever social engineering attack, and one I had not seen before.

From: ((some fake address))

To: schneier@counterpane.com

Subject: Message could not be delivered

Dear user schneier@counterpane.com,

Your email account has been used to send a huge amount of spam messages during the last week. Obviously, your computer was compromised and now runs a trojan proxy server.

Please follow our instruction in the attached file in order to keep your computer safe.

Virtually yours,
counterpane.com user support team.

Posted on November 1, 2004 at 11:44 AMView Comments

News

Last month I wrote: “Long and interesting review of Windows XP SP2, including a list of missed opportunities for increased security. Worth reading: The Register.” Be sure you read this follow-up as well:
The Register

The author of the Sasser worm has been arrested:
Computerworld
The Register
And been offered a job:
Australian IT

Interesting essay on the psychology of terrorist alerts:
Philip Zimbardo

Encrypted e-mail client for the Treo:
Treo Central

The Honeynet Project is publishing a bi-annual CD-ROM and newsletter. If you’re involved in honeynets, it’s definitely worth getting. And even if you’re not, it’s worth supporting this endeavor.
Honeynet

CIO Magazine has published a survey of corporate information security. I have some issues with the survey, but it’s worth reading.
IT Security

At the Illinois State Capitol, someone shot an unarmed security guard and fled. The security upgrade after the incident is — get ready — to change the building admittance policy from a “check IDs” procedure to a “sign in” procedure. First off, identity checking does not increase security. And secondly, why do they think that an attacker would be willing to forge/steal an identification card, but would be unwilling to sign their name on a clipboard?
The Guardian

Neat research: a quantum-encrypted TCP/IP network:
MetroWest Daily News
Slashdot
And NEC has its own quantum cryptography research results:
InfoWorld

Security story about the U.S. embassy in New Zealand. It’s a good lesson about the pitfalls of not thinking beyond the immediate problem.
The Dominion

The future of worms:
Computerworld

Teacher arrested after a bookmark is called a concealed weapon:
St. Petersburg Times
Remember all those other things you can bring on an aircraft that can knock people unconscious: handbags, laptop computers, hardcover books. And that dental floss can be used as a garrote. And, and, oh…you get the idea.

Seems you can open Kryptonite bicycle locks with the cap from a plastic pen. The attack works on what locksmiths call the “impressioning” principle. Tubular locks are especially vulnerable to this because all the pins are exposed, and tools that require little skill to use can be relatively unsophisticated. There have been commercial locksmithing products to do this to circular locks for a long time. Once you get the feel for how to do it, it’s pretty easy. I find Kryptonite’s proposed solution — swapping for a smaller diameter lock so a particular brand of pen won’t work — to be especially amusing.
Indystar.com
Wired
Bikeforums

I often talk about how most firewalls are ineffective because they’re not configured properly. Here’s some research on firewall configuration:
IEEE Computer

Reading RFID tags from three feet away:
Computerworld

AOL is offering two-factor authentication services. It’s not free: $10 plus $2 per month. It’s an RSA Security token, with a number that changes every 60 seconds.
PC World

Counter-terrorism has its own snake oil:
Quantum Sleeper

Posted on October 1, 2004 at 9:40 PMView Comments

News

Last month I wrote: “Long and interesting review of Windows XP SP2, including a list of missed opportunities for increased security. Worth reading: The Register.” Be sure you read this follow-up as well:
The Register

The author of the Sasser worm has been arrested:
Computerworld
The Register
And been offered a job:
Australian IT

Interesting essay on the psychology of terrorist alerts:
Philip Zimbardo

Encrypted e-mail client for the Treo:
Treo Central

The Honeynet Project is publishing a bi-annual CD-ROM and newsletter. If you’re involved in honeynets, it’s definitely worth getting. And even if you’re not, it’s worth supporting this endeavor.
Honeynet

CIO Magazine has published a survey of corporate information security. I have some issues with the survey, but it’s worth reading.
IT Security

At the Illinois State Capitol, someone shot an unarmed security guard and fled. The security upgrade after the incident is — get ready — to change the building admittance policy from a “check IDs” procedure to a “sign in” procedure. First off, identity checking does not increase security. And secondly, why do they think that an attacker would be willing to forge/steal an identification card, but would be unwilling to sign their name on a clipboard?
The Guardian

Neat research: a quantum-encrypted TCP/IP network:
MetroWest Daily News
Slashdot
And NEC has its own quantum cryptography research results:
InfoWorld

Security story about the U.S. embassy in New Zealand. It’s a good lesson about the pitfalls of not thinking beyond the immediate problem.
The Dominion

The future of worms:
Computerworld

Teacher arrested after a bookmark is called a concealed weapon:
St. Petersburg Times
Remember all those other things you can bring on an aircraft that can knock people unconscious: handbags, laptop computers, hardcover books. And that dental floss can be used as a garrote. And, and, oh…you get the idea.

Seems you can open Kryptonite bicycle locks with the cap from a plastic pen. The attack works on what locksmiths call the “impressioning” principle. Tubular locks are especially vulnerable to this because all the pins are exposed, and tools that require little skill to use can be relatively unsophisticated. There have been commercial locksmithing products to do this to circular locks for a long time. Once you get the feel for how to do it, it’s pretty easy. I find Kryptonite’s proposed solution — swapping for a smaller diameter lock so a particular brand of pen won’t work — to be especially amusing.
Indystar.com
Wired
Bikeforums

I often talk about how most firewalls are ineffective because they’re not configured properly. Here’s some research on firewall configuration:
IEEE Computer

Reading RFID tags from three feet away:
Computerworld

AOL is offering two-factor authentication services. It’s not free: $10 plus $2 per month. It’s an RSA Security token, with a number that changes every 60 seconds.
PC World

Counter-terrorism has its own snake oil:
Quantum Sleeper

Posted on October 1, 2004 at 9:40 PMView Comments

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Sidebar photo of Bruce Schneier by Joe MacInnis.