A compromise July 19 resulted in attackers obtaining fraudulent certificates that were indistinguishable from legitimate certificates. Google.com was among the domains for which the phony certificates were issued, the company says.
ANALYSIS: With SSL, who can you really trust?
The certificates can be used to launch man-in-the-middle attacks that compromise communications that SSL was intended to protect.
Action by browser makers means that they will show a warning whenever users access sites that are authenticated only by SSL certificates issued by DigiNotar, which could be an impediment to companies trying to conduct secure transactions with customers.
The attackers who stole the certificates seem to be interested in intercepting Gmail accounts held by customers in Iran, according to Google.
In its statement, Vasco says that multiple fraudulent certificates were issued, and DigiNotar revoked them. But later a Dutch government agency showed that it had missed one of the certs that was then revoked as well.
"The attack was targeted solely at DigiNotar's Certificate Authority infrastructure for issuing SSL and EVSSL certificates," the Vasco statement says. "No other certificate types were issued or compromised. DigiNotar stresses the fact that the vast majority of its business, including his Dutch government business (PKIOverheid) was completely unaffected by the attack."
A similar certificate theft from Comodo in March was carried out from an Iranian IP address and like the DigiNotar theft included certificates for Google's Gmail domain. It also included domains for Mozilla, Yahoo and Skype. At the time, Comodo's CEO said the attack was likely driven by the Iranian government, and Comodo published the IP address from which the theft was made.
The day after the Comodo attack, that same IP address downloaded a man-in-the-middle attack tool, sslsniff, from a website run by security researcher Moxie Marlinspike, who told a Black Hat conference audience about the incident earlier this summer.
With the certificates, attackers can launch man-in-the-middle attacks to intercept secure communications meant for the domains for which false certificates were issued.
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