The largest telecommunications company in the Netherlands has stopped issuing SSL (Secure Sockets Layer) certificates after finding indications that the website used for purchasing the certificates may have been hacked.
The backend infrastructure used to generate certificates does not appear to have been affected, although an investigation is under way with results expected soon, KPN spokeswoman Simona Petescu said on Monday.
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During an audit, the public-facing website showed indications that someone may have tried to prepare it for Distributed Denial-of-Service (DDoS) attacks as long as four years ago, according to a press release issued on Friday by KPN.
It does not appear that any fraudulent SSL certificates have been created, Petescu said. But as a precaution, it stopped issuing certificates and also notified the Dutch government's interior affairs ministry, she said.
KPN's corporate IT services branch, KPN Corporate Market, issues the SSL certificates, which enable a Web browser and website to exchange encrypted information using the SSL protocol.
KPN's Corporate Market is known as an intermediate Certificate Authority, one of hundreds of businesses and organizations around the world that can issue SSL certificates linked backed to a so-called root Certificate Authority.
CAs are a particularly attractive target for hackers. Creating a fraudulent certificate can make it appear a person is visiting a legitimate website when in fact it is not or to intercept information. Security experts have called the current SSL issuing system weak.
Last week, a Malaysian intermediate certificate authority called Digicert revoked 22 of its own certificates due to weak RSA encryption keys and missing certificate extensions. On Thursday, Mozilla and Microsoft revoked all certificates issued by the company.
In August, a Certificate Authority called DigiNotar, which is a subsidiary of Vasco Data Security International, revealed that it had been hacked earlier in the year. Browser makers ended up revoking some 500 fraudulent SSL certificates.
Among the companies affected was Google, which said a fake certificate was used in attempted man-in-the-middle attacks against users of its Gmail service in Iran. The fraudulent certificate would allow a hacker to view information passing between a Gmail user and Google's servers.
DigiNotar filed for bankruptcy in a Dutch court in September.
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