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Investigators Replicate Nokia 1100 Banking Hack

Posted by timothy on from the could-be-an-ebay-scam-rumor dept.

Ian Lamont writes "Investigators have duplicated an online banking hack using a 2003-era Nokia mobile phone. Authorities had been aware for some time that European gangs were interested in buying the phone, and were finally able to confirm why: It can be used to access victims' bank accounts using "special software written by hackers." The hack apparently works by letting criminals reprogram the phones to use someone else's phone number and receive their SMS messages, including mTANs (mobile transaction authentication numbers) from European banks. However, the only phones that work are 1100 handsets (pictures) made in a certain factory. Nokia had claimed last month it had no idea why criminals were paying thousands of euros to buy the old handsets."

57 of 181 comments (clear)

  1. It may be illegal.. by Anonymous Coward · · Score: 4, Interesting

    It may be illegal, but the hackers deserve some credit for being able to figure this out.

    1. Re:It may be illegal.. by OeLeWaPpErKe · · Score: 3, Interesting

      Even now clearly the over-the-air gsm protocol allows for this hack. Perhaps 1100 phones will be in short supply, but clearly the protocol itself is vulnerable.

      If they found the 1100 flaw, how hard could it be to duplicate the flaw in a something like a 800 Mhz tuner + fpga ?

    2. Re:It may be illegal.. by K.+S.+Kyosuke · · Score: 5, Funny

      I guess they think as well that they deserve some credit. That's why they are breaking into a bank.

      --
      Ezekiel 23:20
    3. Re:It may be illegal.. by cbrocious · · Score: 3, Informative

      You don't even need to go the FPGA route. The baseband firmware on the iPhone has been patched for an unlocking, there's nothing stopping someone from patching it to change the IMEI built into the phone or the IMSI it "reads" from the SIM. Change these and the phone can become any other.

      --
      Disconnect and self-destruct, one bullet at a time.
    4. Re:It may be illegal.. by FooAtWFU · · Score: 5, Funny

      I guess they think as well that they deserve some credit. That's why they are breaking into a bank.

      That's debit, silly.

      --
      The World Wide Web is dying. Soon, we shall have only the Internet.
    5. Re:It may be illegal.. by K.+S.+Kyosuke · · Score: 4, Interesting

      If I am not mistaken, you already can buy and run something like that.

      --
      Ezekiel 23:20
    6. Re:It may be illegal.. by Bill,+Shooter+of+Bul · · Score: 2, Insightful

      Depends on your definition of hard. If I were a Criminal I'd be looking at an open moko, to see if you could hack that in a similar manner. The firmware is fully open

      --
      Well.. maybe. Or Maybe not. But Definitely not sort of.
    7. Re:It may be illegal.. by sexconker · · Score: 4, Insightful

      It's not the phone.
      A phone is nothing but a transceiver.

      It's the system we have for identifying phones, and the practice of letting people bank over it (or sending authentication pins for pc banking to phones).

      Using a phone number as a method of authentication is inherently flawed. The practice will continue, however, because the plebes want easy more than they want secure. After all, it'll never happen to them.

    8. Re:It may be illegal.. by cbrocious · · Score: 2, Insightful

      That's the firmware for the application CPU, but I don't believe the GSM baseband chip's firmware is open.

      --
      Disconnect and self-destruct, one bullet at a time.
    9. Re:It may be illegal.. by fuzzyfuzzyfungus · · Score: 3, Informative

      I'm fairly sure that the OpenMoko only achieves that level of firmware openness by integrating a separate GSM module, with which it communicates via standard AT commands. Just as, back in the bad old days of dialup, modems were closed source; and you could either get a winmodem, or a modem with a proper processor of its own.

      Were I a criminal with a technical inclination, I'd be more interested in something like GNU radio, as suggested in this comment

    10. Re:It may be illegal.. by Chelloveck · · Score: 3, Funny

      That's right. People should be required to enter their 1024-bit PGP key by hand every time they make a transaction.

      --
      Chelloveck
      I give up on debugging. From now on, SIGSEGV is a feature.
    11. Re:It may be illegal.. by rtfa-troll · · Score: 5, Informative

      Bullshit. Not on any properly run network. Apart from the IMEI (which is written on the back of the phone) and the IMSI (which you can get with a special code from some phones) there's also the Ki. This is a secret which is buried in the SIM card and _never_ sent out to the phone. Without the physical SIM card in your phone you do not have the number.

      Now, there have been flaws in this; it has been possible to clone the SIM card because of implementation flaws, but properly made new SIMS should not have most of these. The authentication algorithms used originally were weak and could leak the key, but modern SIMs should be using stronger ones (e.g. AES). However none of these were magically to do with one particular model of a phone.

      Something different is going on here. E.g. a security company marketing scam or that the mobile can work as a short range base station and do interception or something else. Definitely not the way that it seems to be explained in the article. And definitely not that the just "changed the IMEI and the IMSI and became the other subscriber"; apart from anything else, you have no need to change the IMEI to do that.

      --
      =~ s,(.*),<sarcasm>$1</sarcasm>,g if any_point_you_wish();
    12. Re:It may be illegal.. by mea37 · · Score: 2, Insightful

      Cell phones don't use the phone number as a method of authentication. Cell phone users use the phone number as a method of identification (when they place a call or send a message to the number).

      The network "looks for" the identified phone so it can deliver the message. Rather, the network looks for a phone that has authenticated as a match for the phone number.

      The process by which the phone authenticates may well be flawed, but this has nothing to do with the end-user simplicity of "phone numbers"; the process is already decoupled from that simplicity as the phone # is not the information used to authenticate the phone on the network.

    13. Re:It may be illegal.. by fuzzyfuzzyfungus · · Score: 3, Informative

      Evidence for above claim:

      " CALYPSO ASIC digital baseband Unfortunately we cannot provide many details on the GSM chipset due to very tight NDAs. However, this is not neccessarily required, since it interfaces using a standard UART serial line with the S3C2442. On that interface, GSM 07.05, GSM 07.10 and other standardized protocols are used. "

    14. Re:It may be illegal.. by olden · · Score: 2, Informative
      Why hide the source of the above quote? Oh yes, because the next paragraph reads:

      "The NDAd documentation for the calypso, register definition (sic) and hardware definition, was leaked [...]"

      Maybe not so un-hackable after all...

    15. Re:It may be illegal.. by cheater512 · · Score: 3, Informative

      In a hash function as a challenge response.

      The tower sends a chunk of data, its sent to the SIM, its then transformed by Ki and then sent back to the tower.
      The tower knows what Ki is and does the same transformation and verifies that the reply is the same.

    16. Re:It may be illegal.. by wvmarle · · Score: 2

      I guess they think as well that they deserve some credit. That's why they are breaking into a bank.

      That's debit, silly.

      Not from the victim's point of view...

  2. Damn... by Jaysyn · · Score: 3, Funny

    I think I had one of those & gave it to my 4 yr old nephew to play with / destroy it.

    --
    There is a war going on for your mind.
    1. Re:Damn... by ObsessiveMathsFreak · · Score: 5, Funny

      You've turned him to a life of crime!!

      --
      May the Maths Be with you!
  3. Hardware hack? by Anonymous Coward · · Score: 5, Interesting

    "The modified firmware is then uploaded to the Nokia 1100. Certain models of the 1100 used erasable ROM, which allows data to be read and written to the chip, Becker said."

    If that's the case, how hard would it be to desolder a non-flashable ROM and replace it with one that is? It would certainly be more hassle than buying a phone already built that way, but with the right tools and enough effort, why wouldn't any phone be susceptible to this type of attack?

    1. Re:Hardware hack? by dave562 · · Score: 4, Informative

      It probably isn't so much just the ROM, but also the code on the phone itself, and the amount of available room in the memory to work with. The hackers probably developed their code specifically for that phone, and are counting on memory addresses being in a particular place, and all sorts of other variables that have to be considered when writing assembly code for a specific piece of hardware.

      Back in the day, everyone wanted an Oki 900 because it could store between 5 and 99 ESN/MIN pairs AND swap them on the fly. In theory, you could just use G2 and reprogram a Motorola flip phone, but that required a laptop and a loader phone. So sure, you could do the same with with a Motorola, but it was a lot easier to use an Oki. In the end though, the result was the same. You were able to make calls and not pay for them.

      In the case of the Nokia phone, whoever developed the hack developed it for the Nokia 1100. They probably spent a lot of time reverse engineering/disassembling the original EEPROM and a lot of time hacking the code together to make it work.

  4. Correct use of the term by kidde_valind · · Score: 2, Interesting

    It's nice to see an example of correct use of "hacker" by the mainstream media, even if it's just by chance

  5. still using one by jaroslav · · Score: 5, Funny

    I've got one of these in my pocket right now. Do you think it would raise any suspicion if I posted it on eBay now?

    Nokia 1100 L000000K! RARE! HACK BANKS!!!

    1. Re:still using one by syousef · · Score: 4, Funny

      Do you think it would raise any suspicion if I posted it on eBay now? Nokia 1100 L000000K! RARE! HACK BANKS!!!

      A++++++ thief. Would steal with him again!

      --
      These posts express my own personal views, not those of my employer
  6. Nokia: 1 - Apple: 0 by Jonas+Buyl · · Score: 5, Funny

    Smart move from Nokia trying to outsell the iPhone

    1. Re:Nokia: 1 - Apple: 0 by kovari · · Score: 3, Informative

      Actually, this particular model outselled iPod. All models.

    2. Re:Nokia: 1 - Apple: 0 by Keruo · · Score: 4, Informative

      Trying to outsell?

      Nokia's one billionth phone sold was a Nokia 1100 purchased in Nigeria.
      (http://www.engadget.com/2005/09/21/nokia-crosses-one-billion-mark/)

      Although something tells me that Nigeria isn't neccessarily most prominent market for apple, since price of an iphone is equal to one years salary for an average nigerian.

      --
      There are no atheists when recovering from tape backup.
    3. Re:Nokia: 1 - Apple: 0 by megamerican · · Score: 2, Funny

      Trying to outsell?

      Nokia's one billionth phone sold was a Nokia 1100 purchased in Nigeria.
      (http://www.engadget.com/2005/09/21/nokia-crosses-one-billion-mark/)

      Although something tells me that Nigeria isn't neccessarily most prominent market for apple, since price of an iphone is equal to one years salary for an average nigerian.

      They seem to have a lot of royalty. Maybe Apple should go after them.

      --
      If you have something that you dont want anyone to know, maybe you shouldnt be doing it in the first place -Eric Schmidt
    4. Re:Nokia: 1 - Apple: 0 by SydShamino · · Score: 5, Funny

      Although something tells me that Nigeria isn't neccessarily most prominent market for apple, since price of an iphone is equal to one years salary for an average nigerian.

      That's just because the average Nigerian's money is caught up in an off-shore bank account, and we aren't doing our part to help them access the funds despite the generous offer of 10% commission.

      --
      It doesn't hurt to be nice.
  7. i doubt it by wjh31 · · Score: 2, Interesting

    they are actually very widespread, i see that model all over the place. Not everyone wants a top of the range phone, some just want to make calls and use texts. This is one of the few dirt cheap phones available.

    1. Re:i doubt it by Achromatic1978 · · Score: 2, Insightful

      Not just any Nokia 1100. One made in a certain factory in a certain date range with a certain revision of the firmware. And how long before you sold such a phone before the police came knocking on your door, wanting that money back (I'm fairly sure that 'hackers wanting a phone for its ability to easily be hacked for online banking' are not actually giving you 25,000 of their own euro...)

    2. Re:i doubt it by Achromatic1978 · · Score: 3, Insightful
      When receiving stolen property, the law looks at what a "reasonable" person would believe. A reasonable person would believe that someone selling on CL/eBay a Samsung 55" 1080p 120Hz LED TV complete with packaging, receipt for warranty purposes for say $2,500 (from an selling prize at Amazon of $3,199) was getting a good, but legitimate deal.

      A reasonable person, in the eyes of the law, would not believe if I came up to them at an outdoor cafe and said "Want a 55" LED TV for $300? Meet me in the parking lot in 5 minutes" that they were buying anything other than illegally obtained or acquired property.

      A reasonable person selling his Nokia 1100 (currently settling in the market for around $70) would assume that if they got, say an offer of $150, that the buyer might be an aficionado of old school cellular technology.

      A reasonable person selling his Nokia 1100 would not "ask no questions" about a bidding war on their phone which saw it run into the five digit territory. A reasonable person would also have doubts about such money, and the motivations of a buyer. Whilst under no obligation to investigate either, a reasonable person, in the eyes of the law, would have "concerns" about whether the payment they were about to receive was the proceeds of a crime, or similar.

  8. They're just reprogramming the IMEI and IMSI... by admiralfrijole · · Score: 4, Interesting

    from tfa: That application allows a hacker to decrypt the Nokia 1100's firmware, Becker said. Then, the firmware can be modified and information such as the IMEI (International Mobile Equipment Identity) number can be changed as well as the IMSI (International Mobile Subscriber Identity) number, which allows a phone to register itself with an operator.

    Uh... this ability is hardly unique to this device, I have a feeling there's something else they're not telling us.

    --
    e to the pi i plus one equals zero
    1. Re:They're just reprogramming the IMEI and IMSI... by Pinky's+Brain · · Score: 2, Interesting

      They are probably eavesdropping only, if complete SIM cloning without physical access was possible with just a modified phone that would be much bigger news than this.

    2. Re:They're just reprogramming the IMEI and IMSI... by internerdj · · Score: 3, Informative

      It was probably just set up so that it was easy to do compared to other phones. When I worked for LG's Cell division there was a hidden password protected menu on some models for changing any of the firmware settings, finding the menu would have been next to impossible but the default password was something similar to 8 0's. While this sounds a bit more complex my guess would be they did something stupid with the flash updater like not put any protections on the firmware downloads.

    3. Re:They're just reprogramming the IMEI and IMSI... by Viraptor · · Score: 5, Interesting

      Agreed - the explanation seems weird. I'm not sure about Nokia patching scene, but most of the Siemens *45, *55, *65 phones could be completely reprogrammed and were well understood. SL45 was one of the best examples - it's annotated assembler firmware was so nice to work with that people simply wrote binary patches in assembler, or used C compiler + binary patched some jump addresses. There were complete design notes circulating on P2P networks. I'm not sure what can be so specific to Nokia 1100 that they don't want to reprogram any other device.

      Even better - if they're good enough to reprogram Nokia to interact directly with SIM and GSM module, why won't they just buy GSM modules themselves and clone some random SIM cards? It's not like GSM transmitters are some controlled goods available only to Nokia et al. If you can afford 100 of them, they should be quite easy to obtain.

      So yeah - it seems there's something more going on here. Or they're just some script kiddies who bought a "hacking technique" from someone more advanced and now they can only replicate the issue on that one device.

    4. Re:They're just reprogramming the IMEI and IMSI... by bhtooefr · · Score: 2, Informative

      Knowing the general gist of how cellular protocols work, I don't think there is anything they're not telling us. It's just that most phones don't have reprogrammable IMEIs, for very obvious reasons.

      Although, I didn't think GSM phones even authenticated via the IMEI normally, just via the info on the SIM, so cloning the SIM would be enough. Guess I was wrong.

      CDMA phones do authenticate via the MEID or ESN (or pESN, an encoded form of the MEID, for backwards compatibility with equipment that can't handle MEIDs,) meaning such an attack would be VERY effective on CDMA. And, a lot of older CDMA equipment has the ESN such that it's not too hard to reprogram with the right software.

  9. the real security defect by Gary+W.+Longsine · · Score: 4, Insightful

    Correct. The real defect here isn't the phone, it's the system it's spoofing. This phone just makes it easier to construct the spoof.

    --
    If you mod me down, I shall become more powerful than you could possibly imagine.
  10. Get them for 5.50 from ebay by sygin · · Score: 2, Interesting

    Bidding has started ...

    http://catalog.ebay.co.uk/Nokia-1100-Mobile-Phone_W0QQ_fclsZ1QQ_pidZ56002720QQ_tabZ3

    --
    Don't make your problems my problems!
  11. Kudos to the Crooks by alta · · Score: 4, Funny

    Here on /. we're always bragging about find good use for old hardware. Well these guys did just that, and now you're going to chastise them for it.

    You people have been asking for us to recycle our electronics for years now, bitching about throwing away cell phones, and their toxic batteries. This guys deserve some sort of award for this.

    Good job
    where can I get one?

    --
    Do not meddle in the affairs of sysadmins, for they are subtle, and quick to anger.
  12. So who will be fired by bugs2squash · · Score: 2, Insightful

    For implementing such a flawed banking transaction protocol.
    Don't bother replying, I know the answer is no-one.

    --
    Nullius in verba
    1. Re:So who will be fired by jimicus · · Score: 5, Insightful

      A number of people in IT seem to believe that the only acceptable form of security - particularly as it relates to anything remotely important - is one which is not susceptible to any sort of attack, real or theoretical, until some time after the heat death of the universe.

      Banks don't. They know full well that there will always be a certain amount of fraud no matter what you do.

      Every change you want to make to the bank's system costs - in man hours to develop, test and deploy the fix and also in terms of the risk of something going wrong when you come to deploy, Most of these costs can be boiled down to cold hard cash. If making the necessary changes will cost more than the amount of fraud it's expected to prevent, don't be surprised to see nothing change.

      Rest assured that these people count cash all day long, they can certainly work out exactly how much such changes will cost.

  13. Re:A certain factory by Acer500 · · Score: 2, Informative

    Is this one particular factory in China, by some chance?

    No, if you happened to read the article you'd find out it was the Bochum, Germany factory.

    --
    There are three kinds of lies: lies, damned lies, and statistics.
  14. Re:Interesting by e4g4 · · Score: 5, Insightful

    I'm guessing it won't take long for these phones to be outlawed in the EU though.

    Yeah, legal prohibition is an excellent way to prevent people from using something. It works so fantastically well for drugs, guns and pirated music/movies.

    --
    The secret to creativity is knowing how to hide your sources. - Albert Einstein
  15. what is needed for this to work...??? by broomer · · Score: 5, Interesting

    1. physical access to SIM-card to get the IMSI
    2. info on bank account / phone number
    3. hacking in PC/internet connection to determine if/when the code is used.
    4. raise no suspicion when a code is sent and not received by the original recipient, and recipient is not able to call/being called or send/receive text because the original phone will be blocked until it is paired again with the GSM-system (power cycled)
    5. you need to have a bank that does have this system. (mine does not)

    so not as viable as it looks.

    1. Re:what is needed for this to work...??? by Reality+Master+201 · · Score: 2, Interesting

      1. physical access to SIM-card to get the IMSI

      Not necessarily - phones transmit the IMSI to the network, and there's known flaws in the encryption scheme GSM uses (and some carriers don't use encryption, though it's not very common, AFAIK). It's plausible that those two would get you the IMSI.

  16. crack bank accounts? by IlluminatedOne · · Score: 5, Funny

    There's an app for that...

    1. Re:crack bank accounts? by Minwee · · Score: 2, Funny

      There's an app for that...

      Yes, and it runs on an Atari Portfolio.

      Easy money.

  17. Just one question: by Hurricane78 · · Score: 2, Insightful

    What crazy bank sends *TANs to mobile phones in the first place?? Even this possibility would be a reason for me to terminate the contract.
    I really recommend chipcard based systems. I use a class 2 terminal, and HBCI. It's not only much more comfortable, it's also on a completely different level in terms of security.
    (In case you do not know how it works: Everything between the chipcard controller and the bank system basically only forwards encrypted packets. And if anything meddles with them, it detects this. You need the card, and a code of six numbers, and the server associates a user with that login. Every transaction that follows this, has to be accepted by the chipcard/terminal. The ones with keypads *and* displays are the most secure, because they show the details of the transaction *on* the terminal, and you have to say ok *with* that terminal. So the only open hole that I know of, is physical tinkering with the card and the terminal. Which still would be pretty hard, but not impossible. But if anyone can do this, I'm fucked anyway. ^^ [Oh, and of course, if you know of any problems with this system, I'm happy to hear them.])

    --
    Any sufficiently advanced intelligence is indistinguishable from stupidity.
  18. the article says cloning a SIM is trivial by YesIAmAScript · · Score: 2, Interesting

    But isn't that actually the tough part? That's the whole key to GSM.

    Cloning a SIM is supposed to be non-trivial and should be nigh-impossible if you cannot get physical access to the person's SIM. I know there was an issue where the secret keys in the SIMs weren't random enough, but that's a long time ago now, newer SIMs are not subject to that problem.

    As to the thing about erasable ROM, I thought something like the iPhone 1G had been completely pwned and should be as subject to an IMEI cloning hack as any of these phones.

    --
    http://lkml.org/lkml/2005/8/20/95
  19. Re:Interesting by codegen · · Score: 3, Insightful

    If all the carriers discontinued service to these models they would render them useless.

    I wasn't aware that the model of the phone was part of the GSM protocol. Even if it was, if you can program the phone to lie about the IEMI or IMSI, then you can program the phone to lie about the phone model to the provider.

    --
    Atlas stands on the earth and carries the celestial sphere on his shoulders.
  20. Nokia DCT4 security by Mulder3 · · Score: 5, Informative

    This article is plain stupid, Nokia 1110 has nothing than other phones in the same Nokia DCT4 family don't have, while DCT4 firmwares can be decrypted, Nokia DCT3 phones(Nokia 3310, etc) are much more well suited for this job, given the fact that already exists an open source(GPL) firmware in C for this devices... And about SIM cloning, YOU CANÂT clone a GSM SIM card in seconds!!!! The most advanced software for clone SIM cards(SimScan - http://users.net.yu/~dejan/) still has to do some brute-force to extract the Ki key, witch is designed to never leave the card, while we can extract IMSI with no problems , to clone a SIM card, you need two values: IMSI and Ki, and without Ki, IMSI is worthless...

    1. Re:Nokia DCT4 security by citizenr · · Score: 2, Informative

      plus you cant extract Ki from new cards, and when I write new I mean last >5 years. No one is using Comp128v1 anymore.

      --
      Who logs in to gdm? Not I, said the duck.
  21. Re:Interesting by mdielmann · · Score: 4, Funny

    I'm guessing it won't take long for these phones to be outlawed in the EU though.

    Yeah, legal prohibition is an excellent way to prevent people from using something. It works so fantastically well for drugs, guns and pirated music/movies.

    Don't forget hookers. I think it's illegal to mention drugs and guns without mentioning hookers. And just to be safe, let's mention blackjack.

    --
    Sure I'm paranoid, but am I paranoid enough?
  22. Oh they do, do they? by hellfire · · Score: 2, Funny

    Rest assured that these people count cash all day long, they can certainly work out exactly how much such changes will cost.

    I would have had faith in that statement before the credit crisis of 2008 took hold.

    --

    "All great wisdom is contained in .signature files"

  23. Re:Interesting by ppanon · · Score: 3, Interesting

    According to the other posts earlier in this thread, the critical thing about this phone is that the firmware is a flashable ROM that can be easily reprogrammed. So the critical thing is that you can easily get this phone to lie, about the phone account used, and about anything else that would be transmitted over the standard GSM protocols. So the GP is correct: locking out the phone type - assuming it was possible, wouldn't do any good because the phone could be reprogrammed to impersonate something else.

    It is extremely unlikely that the existing cell tower/receiver infrastructure could be used to determine that a phone is an 1100 impersonating some other model (or even upgraded to do so). It would be better to spend the development costs on revamping GSM to use a secure handshake protocol with large asymmetric key sizes and non-removable private keys, and securing OOB control channels with AES. Good luck getting police forces and spook agencies to roll over for that one though.

    --
    Laissez lire, et laissez danser; ces deux amusements ne feront jamais de mal au monde. - Voltaire
  24. ING Bank, The Netherlands, for one (optionally!) by Animaether · · Score: 2, Interesting

    The ING Bank, formerly Postbank, in The Netherlands does a TAN over phone, for one, but only optionally*; you have to sign up for it.

    It's actually reasonably secure. You need to log in with username/password first, then you have to set up the transaction, then you have to wait for the TAN by phone, and then enter that. It's quite nice when, say, abroad and you do need to do some banking while abroad. If you're away for a month or more, you might have rent to pay, for example; not everybody accepts 2 months' rent, or allow you to pay upon your return.
    Odds are that you'll have your phone with you - so why lug around another (USB) device, a card, etc. Worse yet, who says you can actually plug a USB device into the internet cafe you happen to be at?

    Combine that convenience with the odds that somebody 1. has your username/password and 2. has a copy of your phone in terms of what would be needed to pull this off, are so tiny that - as per other replies - I think there's something more going on here than just duping the network and getting the TANs intended for another person, somehow; it would be far -more- likely a burglar took your actual phone and found your username/password written down on it or something.

    The networks don't just authenticate the phones here, they will simply -not- allow a second copy of an IMEI on the networks. If that happens, they -will- investigate, triangulate, and send in the forces to find out wtf happened that they got a duplicate IMEI. Obviously that may be different outside of the nl-be region (i.e. I'm not even sure how they handle it in germany; but it was my understanding that practically all networks only allow a single ID and red flags get raised when a duplicate pops up)

    * That said, I don't use it. My phone could die, and I would be f'n stuck until I got a new phone to drop the SIM in. Worse yet, I could lose my phone - which is always a possibility for any goods you take with you everywhere, all the time.

    I just work with the long list of TAN numbers printed out on a sheet of paper** The bank asks me for the TAN number corresponding to a given index, I type it in, transaction completed. The only way for that to be intercepted is for it to be done so somewhere along the snailmail line, and any tampering with the envelope/etc. would be glaringly obvious.
    Yes, that paper can be stolen (which would be noticeable) or even copied, and -if- they then have my login information as well, I'm still screwed. But at least there's no possibility of some manner of 'eavesdropping', short of a high powered telescope aimed at my window from an undisclosed location, and I can't easily 'lose' it as I might a phone, as I'm not carrying that list with me all the time. Slight sacrifice of convenience, but I'll live.

    ** Ideally they would send two pages, one with the indices randomized, one with the TAN numbers, that could then be kept in separate locations and simply overlaid to find the TAN corresponding to an index, but this can be done manually if one were just shy of a tinfoil hat.

    =====

    I have yet to be convinced by anybody that one of those 'calculators' / USB devices + a card + lord knows what else is actually more secure without being glaringly less convenient, than what I'm working with now. But maybe I haven't heard the right arguments yet.