An anonymous reader writes: "An unidentified hacker has breached Bycyklen -- Copenhagen's city bikes network -- and deleted the organization's entire database, disabling the public's access to bicycles over the weekend," reports Bleeping Computer. "The hack took place on the night between Friday, May 4, and Saturday, May 5, the organization said on its website. Bycyklen described the hack as "rather primitive," alluding it may have been carried out "by a person with a great deal of knowledge of its IT infrastructure." Almost 2,000 bikes were affected, and the company's employees have been working for days, searching for bikes docked across the city and installing a manual update to restore functionality. The company is holding a "treasure hunt," asking users to hunt down and identify non-functional bikes.