Brein could also have filed a criminal complaint, the judge said.
ING Bank has a special position that all banks have in the legal and financial transaction system, Rullmann said. Clients should be able to trust their banks and client data should only be communicated in very exceptional circumstances. And if that data should be shared it should be in safe hands, she added.
The court ordered Brein to pay ING's litigation fees of about €1,400 (US$1,800).
Brein disagrees with the decision and will appeal the case, it said in a blog post on Friday.
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