Friends, I decided to step a little on a slippery path
I am not a great specialist in fraudulent operations, but it so happened that I know something about such things. Just spreading such information is not entirely fair ... At the same time, such things are just very interesting in themselves and shed light on what security specialists are faced with, how the industry works, etc. Therefore, today I will venture to tell you about one of the outdated ways to deceive ATMs. I just really like it - it has a certain grace of engineering thought (albeit criminal), I can't help but appreciate it.So listen.
The ATM has several cassettes for notes. For issue - from four to eight (more difficult to fit). There may be denominations of one currency, or there may be several currencies, and in the latter case, four cassettes are clearly not enough. But besides these tapes there are a couple of service tapes. One is for "defective" bills (which, for example, are hushed up, or two have glued together at once, etc. - the ATM itself cannot deal with them, and then it drops these incomprehensible bills into this cassette, reject cassette) ... And then there's another cassette called Retract, and that's what it is for. When someone withdraws money, it is collected from the cassettes and fed to the dispenser. This device opens its armored lid and pops out the bills. But in the ATM, each action has its own timeout, bills will not stick out endlessly outside. After this timeout expires, the ATM will pull these bills back and close the armored cover. It is understood that the customer simply forgot to get the bills from the ATM. An ordinary average ATM does not know how to do anything more with these banknotes, and there may be a set of different denominations. Therefore, these bills are dropped into the same Retract-cassette. If there were several unsuccessful issues, a certain amount of discarded bills will accumulate there.
How does the fraud associated with this mechanism work? Here's the thing. The situation is not the most common, and therefore the dispenser does not know how to determine how many bills have been drawn in. Therefore, the fraudster does this: he orders a pack of bills for delivery, then holds a part of the pack with his fingers (he just holds it, does not pull it out). The ATM waits for the set timeout, then tries to pull the bills back. However, it turns out to be done only with those bills that are not held by the attacker's fingers. The ATM thinks it has pulled in all the bills, dumps them into a retract cassette, and rolls back the transaction. And it turns out that nothing seems to have been removed from the card, but the fraudster has several bills in his hands. He goes to several other ATMs and repeats the trick (after all, the card balance has not decreased).
However, this method is fairly easy to counter ... First, the transaction is no longer rolled back. Secondly, now any ATM, after being dropped into a retract cassette, simply goes into a mode where it either does not allow anything to be done at all, or simply does not give out money (but account information, card payments, etc. continue to work). Then there will be money in the retract cassette associated with a single transaction, and now it is easy to determine whether all the money has returned. If not, it is clear from which card the fraudulent operation and for what amount. And if it is also a card of our bank, then we generally know where the person lives.
And how much money is in the retract-cassette, it turns out at the time of collection.
This is how it works
