I don't get why people would do this ... don't the bank just put their account into a negative balance?

I read about another case in australia where an ATM was issuing $50 notes in place of $20 notes so once word got out a ton of people turned up to withdraw $80 - it came out as 4 x $50s = $200 ... but they were also asked to pay it back to the bank...

http://www.couriermail.com.au/news/commonwealth-bank-atm-dis...

It would have made more sense if they were using stolen ATM cards.

It should be noted that they weren't being charged for withdrawing more than the maximum: they were being charged with attempting to withdraw more money than was in their accounts (apparently with intent to defraud the bank).

I really don't know what they expected to get from this to be honest: I mean, I'm pretty sure when you open the account you recognise somewhere, somehow, that if you overdraw your account it's your responsibility to pay it back...

You can usualy work out when a ATM is in batch mode by the length of time it takes to process. Though as a rule public holidays tend to be the best ones to find a ATM in batch mode as its a great time to update the banking mainframe software and other lovely updates with the least buisness time impact.

Also according to a ISO standard on magnetic cards with used by banks - track 4 as will have stored the last amount taken out. So even if you have say 1000 units of money in your account and take it all out and then try to take it out again, the cashpoint (even in batch mode) will know. Now if you cloned your own card prior to the transaction and then used that clone, you may or may not be able to withdraw that money again - but would also have to use a different ATM is the one you just used will have a record itself.

Bottom line you can defraud banks out of there money, but it involves breaking the law like any other form of imoral gains. Only true way to rob a bank is to be another bank somebody once said, may very well be the thruest and with that sadly the only way legaly.