The UK's Yorkshire Building Society has been put on notice after an unencrypted laptop containing a large customer database was stolen earlier this year.
The UK Information Commissioner's Office (ICO) said the laptop contained a "substantial part" of the bank's database.
According to the ICO, the institution recovered the laptop within 48 hours, and despite passwords for the laptop written on a piece of paper in the laptop bag, the thief apparently was unable to access the data.
"Forensic investigations revealed that none of the data had been accessed during that time, although there had been several attempts to do so," the ICO said in a statement.
The building society has agreed to encrypt all laptop devices, and ensure that when laptops are taken offsite that only staff only have access to data required for work.
Yorkshire Building Society's undertaking was a relative slap on the wrist by the ICO compared to the $4 million fine issued to Zurich by the UK's Financial Services Regulator for losing a tape containing customer details.