Cybercriminals using digitally signed Java exploits to trick users

The lack of default certification revocation checking in Java makes the problem worse, researchers say

By Lucian Constantin, IDG News Service |  Endpoint Security

The exploit found by researchers Monday was signed with a digital certificate that's most likely stolen. The certificate was issued by Go Daddy to a company called Clearesult Consulting based in Austin, Texas, and was subsequently revoked with a date of Dec 7, 2012.

Certificate revocations can apply retroactively and it's not clear when exactly Go Daddy flagged the certificate for revocation. However, on Feb. 25, three days before the oldest sample of this exploit was detected, the certificate was already listed as revoked in the certificate revocation list published by the company, Kubec said. Despite this, Java sees the certificate as valid.

On the "Advanced" tab of the Java control panel, under the "Advanced security settings" category, there are two options called "Check certificates for revocation using Certificate Revocation Lists (CRLs)" and "Enable online certificate validation" -- the second option uses OCSP (Online Certificate Status Protocol). Both of these options are disabled by default.

Oracle does not have any comment about this issue at this time, Oracle's PR agency in the U.K. said Tuesday via email.

"Sacrificing security for convenience is a serious security oversight, especially as Java has been the most targeted third-party piece of software since November 2012," Botezatu said. However, Oracle is not alone in this, the researcher said, noting that Adobe ships Adobe Reader 11 with an important sandbox mechanism disabled by default for usability reasons.

Both Botezatu and Kubec are convinced that attackers will increasingly start using digitally signed Java exploits in order to bypass Java's new security restrictions more easily.

Security firm Bit9 recently revealed that hackers compromised one of its digital certificates and used it to sign malware. Last year, hackers did the same with a compromised digital certificate from Adobe.

Those incidents and this new Java exploit are proof that valid digital certificates can end up signing malicious code, Botezatu said. In this context, actively checking for certificate revocations is particularly important because it is the only mitigation available in case of certificate compromise, he said.

Users who require Java in a browser on a daily basis should consider enabling certificate revocation checking to better protect against attacks exploiting stolen certificates, said Adam Gowdiak, the founder of Polish vulnerability research firm Security Explorations, via email. Security Explorations researchers have found and reported over 50 Java vulnerabilities in the past year.

While users should manually enable these certificate revocation options, many of them will probably not do it considering that they don't even install security updates, Kubec said. The researcher hopes that Oracle will turn on the feature automatically in a future update.

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