"The theft came to light after an anonymous email was sent to the ECB seeking financial compensation for the data. While most of the data were encrypted, parts of the database included email addresses, some street addresses and phone numbers that were not encrypted," the central bank said.
Users whose information might be part of the beach are in the process of being contacted, the ECB said, and advised that all passwords on the system have been changed as a precaution.
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"The ECB takes data security extremely seriously. German police have been informed of the theft and an investigation has started. ECB data security experts have addressed the vulnerability," it said.
The bank is just the latest in a long line of companies and public bodies that have experienced a breach. In May, eBay admitted that hackers had attacked its network and accessed some 145 million user records. It now faces an investigation in the U.S. and the U.K.
Security firms have bemoaned the fact that little is spent on the sector and often companies are left without the skilled workers needed to deal with these situations. Garry Sidaway, the global director of security strategy at NTT Com Security, a risk management solutions firm, told CNBC via email that cyber threats are not going away.
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"The increased global dependency on technology, combined with the evolving complexity of cybersecurity threats, continues to increase our vulnerability at a national, organizational and individual level," he said.
He pointed to a survey conducted by ISACA, a global IT association, in April which estimated that 62 percent of organizations had not increased security training in 2014. The same report also stated that one in five organizations had experienced an APT (Advanced Persistent Threat) attack in the same period.
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