Local cops busted somebody who threatened to derail some trains if he won't get paid. That's a common news. Less common, and more important, detail that the TV news reported confirms the suspicion I had from the beginning of deployment of the prepaid cards technology for local payphones. Each prepaid "Trick" phone card has its unique serial number. The payphone reads it from the card. The busted person (let's call him "target") used the same card for multiple phone calls, thus becoming the card's number known as the target's temporary identity. The interesting part was that the phone company knew in realtime when the card was used - enough in real time to dispatch a police patrol car to the location. Hence, the Trick cards can't be considered as anonymous as coins used to be; at best, they can be used only as pseudonymous-identity tokens. I strongly suspect the usage logs exist for individual cards, allowing to back-trace the phonecalls done with the given card, thus tracing the identity of the card's owner by the call patterns. Suggested countermeasure: When true anonymity is requested, use the card ONLY ONCE, then destroy it. Makes the calls rather expensive, but less risky. Make sure you can't be traced back by other means, ranging from surveillance cameras in the vicinity of the phone booths to the location data from cellphones (because, as it's well-known but often overlooked, the cellphone networks know the location of every active phone). Wondering if there are any records of the UIDs for the cards paired with the locations of the vendor outlets the cards were shipped to.
At 7:51 PM +0100 3/26/04, Thomas Shaddack wrote:
I strongly suspect the usage logs exist for individual cards, allowing to back-trace the phonecalls done with the given card, thus tracing the identity of the card's owner by the call patterns.
Of course.
How do you think they caught the Oklahoma City bombers?
:-).
Cheers,
RAH
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R. A. Hettinga
Nichols was dumb enough to actually be caught in possession of a card used in at last part of the conspiracy. Other cards that seem to be linked to Nichols were used to locate or obtain ANFO and call the rental agency for the Ryder truck as well as other numbers linked to the crime. That is public knowledge at this point. Clearly, logs are available to law enforcement vis-a-vis pre-paid calling cards when they wish to use them. Given the time between the bombing and the capture of at least one of the cards (3-4 days) I suspect those logs are available for at least a few days. Given that the prosecutors claim to be able to link the ANFO purchase via calling cards it is probably a lot longer. What is confusing are the reports that the calling card (or one of them) "bore the name Daryl Bridges." Pre-paid cards don't have names imprinted on them. They would have to have a spot to write them in deliberately. I haven't seen this on any and why would anyone (particularly as part of a criminal conspiracy) do such a thing? Keeping calling cards from leaking information probably isn't possible. Limiting the information leaked to that which is already known or is useless is probably the best bet. Using separate cards for separate operations / cells and immediate disposal seems pretty critical. Note something else, however. I haven't heard of any instances of real time calling card interception. One was described here on the list but that presupposes that a degree of surveillance already exists around the subject. All bets are pretty much off in that event. Calling cards are "after the fact" evidence, not preventative evidence.
-----Original Message----- From: owner-cypherpunks@minder.net [mailto:owner-cypherpunks@minder.net] On Behalf Of R. A. Hettinga Sent: Friday, March 26, 2004 7:10 PM To: Thomas Shaddack; Cypherpunks Subject: Re: Anonymity of prepaid phone chip-cards
I strongly suspect the usage logs exist for individual cards, allowing to back-trace the phonecalls done with the given card, thus
At 7:51 PM +0100 3/26/04, Thomas Shaddack wrote: tracing the
identity of the card's owner by the call patterns.
Of course.
How do you think they caught the Oklahoma City bombers?
And yet one would've thought that a smart radical would have been able to
purchase a measly couple of 50 lb bags of (NH4NO3) without having to call
all over the place and brag about it, and for cash at that. You don't want
it known, don't say it on the phone..
Just like a bunch o' pussys that'll crack the first time they fall into the
clutches of the man.
-Max
At 09:39 PM 3/26/2004, "Black Unicorn"
Nichols was dumb enough to actually be caught in possession of a card used in at last part of the conspiracy.
Other cards that seem to be linked to Nichols were used to locate or obtain ANFO and call the rental agency for the Ryder truck as well as other numbers linked to the crime.
That is public knowledge at this point. Clearly, logs are available to law enforcement vis-a-vis pre-paid calling cards when they wish to use them. Given the time between the bombing and the capture of at least one of the cards (3-4 days) I suspect those logs are available for at least a few days. Given that the prosecutors claim to be able to link the ANFO purchase via calling cards it is probably a lot longer.
What is confusing are the reports that the calling card (or one of them) "bore the name Daryl Bridges." Pre-paid cards don't have names imprinted on them. They would have to have a spot to write them in deliberately. I haven't seen this on any and why would anyone (particularly as part of a criminal conspiracy) do such a thing?
Keeping calling cards from leaking information probably isn't possible.
Limiting the information leaked to that which is already known or is useless is probably the best bet. Using separate cards for separate operations / cells and immediate disposal seems pretty critical.
Note something else, however. I haven't heard of any instances of real time calling card interception. One was described here on the list but that presupposes that a degree of surveillance already exists around the subject. All bets are pretty much off in that event. Calling cards are "after the fact" evidence, not preventative evidence.
-----Original Message----- From: owner-cypherpunks@minder.net [mailto:owner-cypherpunks@minder.net] On Behalf Of R. A. Hettinga Sent: Friday, March 26, 2004 7:10 PM To: Thomas Shaddack; Cypherpunks Subject: Re: Anonymity of prepaid phone chip-cards
I strongly suspect the usage logs exist for individual cards, allowing to back-trace the phonecalls done with the given card, thus
At 7:51 PM +0100 3/26/04, Thomas Shaddack wrote: tracing the
identity of the card's owner by the call patterns.
Of course.
How do you think they caught the Oklahoma City bombers?
At 01:51 PM 3/26/2004, Thomas Shaddack
Suggested countermeasure: When true anonymity is requested, use the card ONLY ONCE, then destroy it. Makes the calls rather expensive, but less risky. Make sure you can't be traced back by other means, ranging from surveillance cameras in the vicinity of the phone booths to the location data from cellphones (because, as it's well-known but often overlooked, the cellphone networks know the location of every active phone).
Better yet, take another 10 minutes, get change from a laundromat, and use coins! Leather gloves, and avoid the cams (hats & sunglasses)! Of course, I'm assumin' a fixed payphone, so the cell phone worries, not to worry... -Max
At 10:51 AM 3/26/2004, Thomas Shaddack wrote:
Each prepaid "Trick" phone card has its unique serial number. The payphone reads it from the card. The busted person (let's call him "target") used the same card for multiple phone calls, thus becoming the card's number known as the target's temporary identity.
What do you mean by "Trick"? Is that a local brand name, or are you implying there's something special about this card? Normal phone cards let their issuers know in almost-real-time that they're being used, because they're spending money from a specific debit account, not digital cash tokens. It's not like old-fashioned monthly phone bills, which didn't need to be in real-time because they knew where you lived (and weren't real money anyway*, except for international calls requiring settlements.) Some cards have more information - many brands can be recharged using a credit card, which might identify the user.
The interesting part was that the phone company knew in realtime when the card was used - enough in real time to dispatch a police patrol car to the location. ... I strongly suspect the usage logs exist for individual cards, allowing to back-trace the phonecalls done with the given card, thus tracing the identity of the card's owner by the call patterns.
Well, of course - databases are much easier these days now that megabits/second and gigahertz are slow and terabytes are small and cheap, and calling card companies _are_ fundamentally in the business of doing database queries and updates, not telecommunications. They're even easier for new competitive phone companies than for the old monopolies, because they don't have an embedded base of antique data structures. An initial call to someone might not be easily traced in near-real-time, unless the recipient was a "usual suspect" set up for it, because that's backwards from the normal database structures. But once you've done the medium or hard work to identify the source of the call after the fact, and gotten lucky by finding it was from a phone card company in your country, setting up a forward trace for future calls from that company shouldn't be very difficult. It's the kind of feature that might only be useful to police and other stalkers, but maybe the phone company had operational reasons for building it, and it looks for data in the Simple Matter of Programming direction, not the Huge Difficult Sieve Through Everything direction. Bill Stewart
Thomas Shaddack wrote: [...]
Suggested countermeasure: When true anonymity is requested, use the card ONLY ONCE, then destroy it. Makes the calls rather expensive, but less risky. Make sure you can't be traced back by other means, ranging from surveillance cameras in the vicinity of the phone booths to the location data from cellphones (because, as it's well-known but often overlooked, the cellphone networks know the location of every active phone).
In local pubs round where I live it is not at all uncommon to find people buying & selling SIM cards, swapping them, or just handing roudn to friends & family members. If these persons are involved in activities which would be disapproved of by the law, I imagine that they would be very unlikley to be anything that could be called terrorism. More likely doing casual work without paying tax, using drugs deprecated by governments, trading in unauthorised DVDs, perhaps employing illegal immigrants. (Allegedly that is - as far as I am aware the apparently oriental gentleman who walks round pubs and clubs late at night offering DVDs and CDs for a pound is in full complience with all local copyright laws) There was a notorious murder locally (Damilola Taylor) which the police took a logn time to charge anywone for. When they finally got round to it, some of the evidence turned on mobile phone records. One piece could not be used, because the court was satisfied that the family and friends of the accused persons swapped and shared phones so frequently that there was no way to connect the use of a phone with an individual.
participants (6)
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baudmax23＠earthlink.net -
Bill Stewart -
Black Unicorn -
ken -
R. A. Hettinga -
Thomas Shaddack