Can bank information be obtained non-officially?
Yes, it has to be admitted that such information can also be obtained by other methods: by illegal action, through negligence, carelessness, or omission, in a hacker attack etc.
Non-legal actions include possible information leaks due to human factor (for example, a personal relationship between a bank officer and a law-enforcement agency official); application of pressure mechanisms or having insiders in various structures. Besides, the hi-tech age offers a variety of methods to get information using special devices (tapping, computer viruses, hacker attacks), as well as surveillance of employees of commercial organisations that are of interest.
Although the information obtained in this way cannot serve as evidence in court, the law-enforcement authorities can use it in further official investigations.