Several copies of the leaked files are now circulating on the internet.

Ficora’s head of networks and security, Erka Koivunen, says people whose personal details were published online should wait for the responsible party to contact them.

The leaked data may have originated from about 10 adult education organisations, according to Ficora. It has not released their names. So far two groups have said their membership lists were involved. They are Suomen Opiskelija-Allianssi OSKU (the Finnish Student Alliance) and Työtehoseura (TTS), a research, development and training institute.

On Saturday, news came to light that more than 16,000 Finns' data were leaked on a file-sharing website. Social security numbers, home addresses, telephone numbers and email addresses were among the data posted online.

Online identity theft

Sites are now popping up claiming to offer a service for people to check if their personal information has been compromised. But Ficora says this is a scam by online predators to steal more valuable information.

“Never type your social security number into a service that offers to reference your information,” says Koivunen.

Data security expert Mikko Hyppönen meanwhile says he suspects that careless handling of information could lie behind the data breach.

The National Bureau of Investigation has launched a criminal investigation into the leak and is expected to announce its findings on Monday.