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Inside 'Operation Black Tulip': DigiNotar hack analysed

CA systems falsely told Iranians they were secure

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The Google webmail of as many as 300,000 Iranians may have been intercepted using fraudulently issued security certificates made after a hack against Dutch certificate authority outfit DigiNotar, according to the preliminary findings of an official report into the megahack.

Fox-IT, the security consultancy hired to examine the breach against DigiNotar, reveals that DigiNotar was hacked on or around 6 June – a month before hackers begun publishing rogue certificates.

Between 10 July and 20 July hackers used compromised access to DigiNotar's systems to issue rogue 531 SSL certificate for Google and other domains, including Skype, Mozilla add-ons, Microsoft update and others. DigiNotar only began revoking rogue certificates on 19 July and waited more than a month after this to go public. The fake *.google.com certificate – which was valid for code-signing – wasn't revoked until 29 July.

The compromise was used, in part, to spy on Iranian internet users, using the forged Google SSL certificate to run man-in-the-middle attacks. Fox-IT found that the vast majority of queries against DigiNotar's OCSP servers (which browsers check to see if a certificate has been revoked) came from Iran during the attack period, unlike periods before and after the attack when the volume of such queries from Iran was negligible.

Many requests not originating from Iran appear to have originated via Tor exit nodes or other proxies used by Iranians in a bid to circumvent net censorship controls.

Shortcomings

The audit reveals a catalogue of security shortcomings at the small previously obscure Dutch certificate authority that allowed the hack to take place.

DigiNotar's servers ran out-of-date software. Its network was poorly segmented, so problems would not be contained if they arose. Passwords in play at the time of the hack might easily have been guessed via brute-force attack. In addition, there was no secure logging and server-side anti-virus protection was absent.

DigiNotar's shocking ineptness in securing its system, compounded with its failure to come clean on its problems in a timely fashion, have turned the firm into a security pariah.

Fox-IT said the hack used hacking tools such as Cain & Abel as well as a variety of custom scripts to pull off the attack. The security agency suggests links between the DigiNotar hack and an earlier attack on Comodo, another certificate authority, back in March.

"We found that the hackers were active for a longer period of time," the Fox-IT report concludes. "They used both known hacker tools as well as software and scripts developed specifically for this task. Some of the software gives an amateurish impression, while some scripts, on the other hand, are very advanced. In at least one script, fingerprints from the hacker are left on purpose, which were also found in the Comodo breach investigation of March 2011. Parts of the log files, which would reveal more about the creation of the signatures, have been deleted.

"The list of domains and the fact that 99 per cent of the users are in Iran suggest that the objective of the hackers is to intercept private communications in Iran," it adds.

DigiNotar's shocking ineptness has turned it into a security pariah

Fox-IT's investigation into the Operation Black Tulip attacks against DigiNotar continues. Trust in all certificates issued by DigiNotar has already been revoked by many browser and operating system developers (including Microsoft, Google and Mozilla but not Apple).

A DigiNotar-controlled intermediate, operationally separate from the SSL business directly hit by the breach, had been issuing certificates as part of the Dutch government’s public key infrastructure "PKIoverheid" scheme. DigiNotar was only one of the available CAs. The Dutch government initially said that the PKIoverheid certs issued by DigiNotar were OK but has since changed its stance over the weekend and ditched DigiNotar from the programme.

In a statement issued on Tuesday in the wake of the damning Fox-IT audit, Vasco (which acquired DigiNotar in January) said the problems with its CA subsidiary had no effect on its core Digipass authentication technology.

"The integration of DigiNotar technology into Vasco’s products was planned for 2012. This means that all Vasco products in the market today are 100 per cent DigiNotar-free. Your authentication project is safe with Vasco," the company asserted.

"Vasco does not expect that the DigiNotar security incident will have a significant impact on the company’s future revenue or business plans," it added. ®

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