Tracking PCs anywhere on the Net

A University of California researcher says he has found a way to identify computer hardware remotely, a technique that could potentially unmask anonymous Web surfers by bypassing some common security techniques.

Tadayoshi Kohno, a doctoral student, wrote in a paper on his research: "There are now a number of powerful techniques for remote operating system fingerprinting, that is, remotely determining the operating systems of devices on the Internet. We push this idea further and introduce the notion of remote physical device fingerprinting...without the fingerprinted device's known cooperation."

The potential applications for Kohno's technique are far-reaching. For example, it could be possible to track "a physical device as it connects to the Internet from different access points, counting the number of devices behind a NAT even when the devices use constant or random IP identifications, remotely probing a block of addresses to determine if the addresses correspond to virtual hosts."

NAT, or network address translation, is a protocol commonly used to make it appear as if machines behind a firewall all retain the same IP address on the public Internet.

Kohno's research is likely not the last word in Net anonymity, but simply the latest escalation in the arms race between snoopware and anonymity developers. Possible countermeasures include masking time skews with better random number generation techniques, for example.

Carnivore-like project?
Kohno appears to be aware of the interest from surveillance groups that his techniques could generate, saying in his paper: "One could also use our techniques to help track laptops as they move, perhaps as part of a Carnivore-like project." Carnivore was Internet surveillance software built by the Federal Bureau of Investigation. Earlier in the paper Kohno mentioned possible forensics applications, saying that investigators could use his techniques "to argue whether a given laptop was connected to the Internet from a given access location."

Another application for Kohno's technique could be to "obtain information about whether two devices on the Internet, possibly shifted in time or IP addresses, are actually the same physical device."

The technique works by "exploiting small, microscopic deviations in device hardware: clock skews." In practice, Kohno's paper says, his techniques "exploit the fact that most modern TCP stacks implement the TCP timestamps option from RFC 1323 whereby, for performance purposes, each party in a TCP flow includes information about its perception of time in each outgoing packet. A fingerprinter can use the information contained within the TCP headers to estimate a device's clock skew and thereby fingerprint a physical device."

Kohno goes on to say: "Our techniques report consistent measurements when the measurer is thousands of miles, multiple hops, and tens of milliseconds away from the fingerprinted device, and when the fingerprinted device is connected to the Internet from different locations and via different access technologies. Further, one can apply our passive and semi-passive techniques when the fingerprinted device is behind a NAT or firewall."

And the paper stresses that "the fingerprinter does not require any modification to or cooperation from the fingerprintee." Kohno and his team tested their techniques on many operating systems, including Windows XP and 2000, Mac OS X Panther, Red Hat and Debian Linux, FreeBSD, OpenBSD and even Windows for Pocket PCs 2002.

"In all cases," the paper says, "we found that we could use at least one of our techniques to estimate clock skews on the machines and that we required only a small amount of data, although the exact data requirements depended on the operating system in question."

A wider test of the techniques also proved fruitful for the researchers. "We also measured the clock skews of 69 (seemingly identical) Windows XP SP1 machines in one of our institution's undergraduate computing facilities. The latter experiment, which ran for 38 days, as well as other experiments, show that the clock skew estimates for any given machine are approximately constant over time, but that different machines have detectably different clock skews," the paper said.

The paper concludes that "the main advantage of our techniques...is that our technique can be mountable by adversaries thousands of miles and multiple hops away."

Information about the technique came to light when KC Claffy, principal investigator for the Cooperative Association for Internet Data Analysis (CAIDA) forwarded information about the project to a mailing list, "in the interest of full and early disclosure." However Claffy also said in her e-mail: "Please don't forward to any bad guys." Kohno is also associated with CAIDA.

Kohno's research is expected to be presented at the Institute of Electrical and Electronics Engineers Symposium on Security and Privacy in California in May.

Renai LeMay of ZDNet Australia reported from Sydney.

[telephonics]

PC Identification

Assuming that the Islamic terrorists utile the internet for communicating with each other this technology might has application to tracking the key leaders and ultimately assist in eliminating them.

[telephonics]

PC Identification

Assuming that the Islamic terrorists utile the internet for communicating with each other this technology might has application to tracking the key leaders and ultimately assist in eliminating them.

Tadayoshi Kohno Thanks for nothing!

Cool say goodbye to our routers, say hello to paying for each device behind it.

[scioara]

There is a will ... there is a way

Short term you might be right. But, what's to stop me from tweaking my NAT's/router's/etc's TCP/IP stack to "play" with the info on which his detection method relies?

Tadayoshi Kohno Thanks for nothing!

Cool say goodbye to our routers, say hello to paying for each device behind it.

[scioara]

There is a will ... there is a way

Short term you might be right. But, what's to stop me from tweaking my NAT's/router's/etc's TCP/IP stack to "play" with the info on which his detection method relies?

No Different from a Virus

"Kohno's research is likely not the last word in Net anonymity, but simply the latest escalation in the arms race between snoopware and anonymity developers. Possible countermeasures include masking time skews with better random number generation techniques, for example."

Wonderful, so now some hotshot has created a way for fraudsters to get into my network. This is no different than a virus. Hopefully some firewall provider will figure out how to prevent this junk from profilerating. What's inside my firewall is intended to remain inside, we've got enough problems as is with viruses and spyware, and I don't need more hacker snoopware intruding on my business operations.

No Different from a Virus

"Kohno's research is likely not the last word in Net anonymity, but simply the latest escalation in the arms race between snoopware and anonymity developers. Possible countermeasures include masking time skews with better random number generation techniques, for example."

Wonderful, so now some hotshot has created a way for fraudsters to get into my network. This is no different than a virus. Hopefully some firewall provider will figure out how to prevent this junk from profilerating. What's inside my firewall is intended to remain inside, we've got enough problems as is with viruses and spyware, and I don't need more hacker snoopware intruding on my business operations.

[Marcus Westrup]

I have my doubts

It may sound good on paper, and even work in a controlled lab setting, but the real world is not so accommodating. Too many factors need to stay constant - thermal variations in the clocking circuit alone will change the results.

With many millions of devices on the net, there are too many signals and not enough skew bandwidth to do any serious tracking outside of a single building.

Wireless on the other hand . . .

[Marcus Westrup]

I have my doubts

It may sound good on paper, and even work in a controlled lab setting, but the real world is not so accommodating. Too many factors need to stay constant - thermal variations in the clocking circuit alone will change the results.

With many millions of devices on the net, there are too many signals and not enough skew bandwidth to do any serious tracking outside of a single building.

Wireless on the other hand . . .

[peterb]

real world test

use the new technique to pinpoint bin laden!

[peterb]

real world test

use the new technique to pinpoint bin laden!

[Jim Hubbard]

Proxies defeat this easily......

Using a proxy to request pages on your behalf is a simple (and free) way to defeat this supposed new threat to privacy. While NATs pass your TCP package through and may be vulnerable to this hack, proxies (when properly done) send their own requests on your behalf - easily defeating this little spoof of TCP.

[Jim Hubbard]

Proxies defeat this easily......

Using a proxy to request pages on your behalf is a simple (and free) way to defeat this supposed new threat to privacy. While NATs pass your TCP package through and may be vulnerable to this hack, proxies (when properly done) send their own requests on your behalf - easily defeating this little spoof of TCP.

[Raife]

Far too simplistic

Yet again, another 'method' which will apparently only work on the 'innocent', the 'ignorant', or someone who is just flat-out not trying to hide their 'identity' in the first-place, ...because simply stripping, or otherwise altering the relevant 'TCP'-headers, either directly through software, ...or by using a 'Proxy', ...or using different software-configurations, ...etc, ...etc, ...etc, ...would all seem to automatically defeat this 'hypothetical' ID-method.

And frankly, it appears that these so-called "fingerprints", most probably, are more a characteristic of 'wishful-thinking' than a truly practical 'hardware-identification' technique (though honestly, I can see, so-called, "...experts for the prosecution" managing to get 'convictions' based upon lengthy 'techno-babble' which falsely proclaims, "...the possibility of an incorrect identification" to be, "...one in a ka-gillion").

Furthermore, I could even see how easy it would be to 'frame' somebody else for a 'crime', simply by identifying, and then 'duplicating', their 'unique hardware-fingerprint'. ...Oh, the possibilities.

But seriously, there are far more serious, and direct, threats to 'anonymity' and 'privacy' afoot in the 'digital-world', these days, than this particular highly-questionable 'student-supposition' (just look-up "Trusted Computing", "DRM", or "BIOMETRIC-ID Authentication").

[Raife]

Far too simplistic

Yet again, another 'method' which will apparently only work on the 'innocent', the 'ignorant', or someone who is just flat-out not trying to hide their 'identity' in the first-place, ...because simply stripping, or otherwise altering the relevant 'TCP'-headers, either directly through software, ...or by using a 'Proxy', ...or using different software-configurations, ...etc, ...etc, ...etc, ...would all seem to automatically defeat this 'hypothetical' ID-method.

And frankly, it appears that these so-called "fingerprints", most probably, are more a characteristic of 'wishful-thinking' than a truly practical 'hardware-identification' technique (though honestly, I can see, so-called, "...experts for the prosecution" managing to get 'convictions' based upon lengthy 'techno-babble' which falsely proclaims, "...the possibility of an incorrect identification" to be, "...one in a ka-gillion").

Furthermore, I could even see how easy it would be to 'frame' somebody else for a 'crime', simply by identifying, and then 'duplicating', their 'unique hardware-fingerprint'. ...Oh, the possibilities.

But seriously, there are far more serious, and direct, threats to 'anonymity' and 'privacy' afoot in the 'digital-world', these days, than this particular highly-questionable 'student-supposition' (just look-up "Trusted Computing", "DRM", or "BIOMETRIC-ID Authentication").

[Andrew J Glina]

Clocks Skews

What happens if the computer updates it's clock via the internet every 10 minutes? Besides, as another person says, this might work for 10, 100 or even 1000 computers. But when it has to track millions of computers....

[Andrew J Glina]

Clocks Skews

What happens if the computer updates it's clock via the internet every 10 minutes? Besides, as another person says, this might work for 10, 100 or even 1000 computers. But when it has to track millions of computers....

[Skippy3246]

Just wait until the hackers start using this "wonderful" technology

This is just great! just what we all need. When the malware writers get a hold of this, they then utilize it to hack through our hardware and software firewalls. Then they can REALLY start delivering spam to our computers. I can hardly wait!!

[Skippy3246]

Just wait until the hackers start using this "wonderful" technology

This is just great! just what we all need. When the malware writers get a hold of this, they then utilize it to hack through our hardware and software firewalls. Then they can REALLY start delivering spam to our computers. I can hardly wait!!

[agottschald]

Sounds just a bit far fetched

Just how many computers are connected to the internet at some time? How many of each model ever made could be connected? When you have say a laptop made by Dell could this method pick out one out of all of the units of a particular model that have been made?

And if like me they switch between wired and wireless cards, not to count all of the cards that over time got damaged and had to be replaced, would the "fingerprint" remain the same?

I've noticed that my laptop clock isn't that great and since the laptop is reletively old, when pushing it on a task I've noticed the system clock loses time. The actual clock which is far from being the best time keeper, varies in time keeping dependent on temperature during idle use and even more during normal use. I just can't see that it would be possible to track a system with this method in the real world, like someone else said the real world is a very different place to a lab.

There is also where you are capturing the packets, if you are capuring the packets at your own site you have an advantage but if you are expecting to intercept packets somewhere in cyberspace, you may never even see them. Nice theory but there are more reliable ways of tracking someone especially if they are accessing your site. In cyberspace, you'd have better chances of winning the meggaball!

[agottschald]

Sounds just a bit far fetched

Just how many computers are connected to the internet at some time? How many of each model ever made could be connected? When you have say a laptop made by Dell could this method pick out one out of all of the units of a particular model that have been made?

And if like me they switch between wired and wireless cards, not to count all of the cards that over time got damaged and had to be replaced, would the "fingerprint" remain the same?

I've noticed that my laptop clock isn't that great and since the laptop is reletively old, when pushing it on a task I've noticed the system clock loses time. The actual clock which is far from being the best time keeper, varies in time keeping dependent on temperature during idle use and even more during normal use. I just can't see that it would be possible to track a system with this method in the real world, like someone else said the real world is a very different place to a lab.

There is also where you are capturing the packets, if you are capuring the packets at your own site you have an advantage but if you are expecting to intercept packets somewhere in cyberspace, you may never even see them. Nice theory but there are more reliable ways of tracking someone especially if they are accessing your site. In cyberspace, you'd have better chances of winning the meggaball!