The forged certificate has been revoked only yesterday, which means that whoever was behind these attacks had the ability to trick users into believing that they were securely accessing any of the SSL-based Google services for more than a month.
Speculations abound about who might be behind the attacks, and given that Iranian users have seemingly been particularly targeted, it is believed by some that the Iranian government is the culprit - especially because this type of attack can usually be successfully executed only if the attacker has a measure of control over the network.
The second reason to suspect them is the fact that the forged certificate was issued for Google and its services, and Gmail is often used by political dissidents all over the world.
The attack was spotted thanks to a Chrome warning that popped up for Iranian user that uses the Chrome browser when he tried to login to his Gmail account. The warning was shown because of a new security feature introduced in Chrome 13. Called certificate pinning, it makes it so that when forcing HTTPS for a domain, only a more trusted subset of CAs are permitted to identify it.
Since DigiNotar has yet to reveal how the rogue certificate has been issued - Was it tricked into doing it? Was it and its root certificate compromised? - and since many browsers do not automatically check for revoked certificates, Microsoft, Mozilla and Google have taken steps to prevent further attacks.
According to Sophos, Mozilla has announced the release of new versions of their browser, mail client and Internet suite in which trust of DigiNotar's root certificate will be revoked.
Microsoft has decided to remove the DigiNotar root certificate from the Microsoft Certificate Trust List, and to release a future update to address this issue for all supported editions of Windows XP and Windows Server 2003. Google has also marked DigiNotar as untrusted in the upcoming release of the Chrome OS.
As with the compromise of a Comodo affiliate Registration Authority and the consequent issuing of rogue SSL certificates issued for a number of high-profile sites back in March, this incidents agains shows that the current CA infrastructure is inherently faulty and not worthy of being trusted, and that we need another solution for the Internet authentication problem.