Weird news - Hacking into a bank without any special skills

Banks routinely tout their extra high security, with most instances talking about bit length (256 and above) encryption keys. Given the nature of business that banks are involved in, ensuring that there is a high amount of security is also critical. Also, given today's fast paced world, there is a need for banks to ensure that they remain on all the time, with no delays. A downtime can cause problems to many customers of the bank, and can cause them to take their business to other banks along with penalties to the bank concerned, especially if their security measures are not as strong as they should be.
So what do you do when it seems that a person can stop a bank's operations or trigger a stoppage on the operations of the bank, such as in this case when a person called into a number that was tied to a back end service machine in the bank and entered some codes that caused the software to trigger an alarm and stoppage of services. The person was arrested by the police, but finally exonerated by the court after there was no malice detected in the 'hack' (link to article):

A Frenchman has been cleared of wrongdoing after a court accepted he accessed the Bank of France's internal telephone systems by accident. An unnamed 37-year-old Breton longed to avoid premium-rate calls while using Skype back in 2008, and set about hunting for a cheap-rate gateway number to the public networks. Judges sitting in a criminal court of Rennes, northwest France, dismissed the case against the man on Thursday, citing the prosecution team's failure to demonstrate any criminal intent in his actions.