Mobile company Nokia was reportedly forced to pay millions of euros to hackers who threatened to release the encryption key of its Symbian operating system.
According to Finnish television station MTV, the incident is believed to have taken place at the end of 2007, when the firms' smartphone market share stood at around 50 per cent.
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The case is currently being looked at by the National Bureau of Investigation.
The encryption key is believed to have been used to ensure that external applications could not be accepted without Nokia's approval.
If the key had been leaked, it would have enabled cybercriminals to create apps containing malware and malicious code that would appear to users as legitimate Symbian apps and updates.
Nokia's huge smartphone market share at the time, coupled with the fact that the operating system was used by other manufacturers, means a huge number of users could have been affected.
Detective Chief Inspector Tero Haapala of the Finnish National Bureau of Investigation was unwilling to reveal many details about the case, but did confirm that it remains unsolved.
"We are investigating felony blackmail, with Nokia the injured party," he said
It is believed that the cash was left in a car park in Tampere, Finland, but the police were unable to keep track of it.