Researchers have discovered malware circulating in the wild that uses a private signing certificate belonging to the Malaysian government to bypass warnings many operating systems and security software display when end users attempt to run untrusted applications.
The stolen certificate belongs to the Malaysian Agricultural Research and Development Institute, according to Mikko Hypponen, chief research officer of F-Secure, the Finnish security firm that found it was being used to sign malware spread using booby-trapped PDF files. By using the official credential to vouch for the trustworthiness of the malicious application, the attackers were able to suppress warnings Microsoft Windows issues when users attempt to install unsigned applications.
"The malware itself has been spread via malicious PDF files that drop it after exploiting Adobe Reader 8," Hypponen wrote in a blog post published on Monday. "The malware downloads additional malicious components from a server called worldnewsmagazines.org. Some of those components are also signed, although this time by an entity called www.esuplychain.com.tw."
The discovery is the latest reminder of the challenges posed in securing the PKI, or public key infrastructure, used to digitally ensure the authenticity and integrity of websites and applications. With more than 600 entities entrusted to issue the certificates, all it takes is the compromise of one of them for an impostor to obtain the private key needed to issue counterfeit credentials for Google, eBay, the Internal Revenue Service or virtually any other service.
Over the past couple years, a growing number of private keys have been abused. One of the best known examples was the Stuxnet worm that sabotaged Iran's nuclear program. It used pilfered digital keys belonging to two companies from Taiwan. The Duqu malware, which some researchers say has significant similarities to Stuxnet, also used private certificates.
Hackers recently compromised the systems of Netherlands-based certificate authority DigiNotar and minted counterfeit credentials for half a dozen sites, including Mozilla's addons website and Skype. A bogus certificate for Gmail was used to spy on about 300,000 people accessing the service from Iran.
Two weeks ago, credentials issued by intermediate certificate authority Digicert Malaysia were banished from major browsers following revelations the company issued secure sockets layer certificates that could be used to attack people visiting Malaysian government websites. A day later, Netherlands-based KPN Corporate Market said it suspended the issuance of new certificates after discovering a security breach that allowed hackers to store attack tools on one of its servers.
The compromised certificate discovered by F-Secure shows the signer as anjungnet.mardi.gov.my. It expired at the end of September. Hypponen said Malaysian authorities have indicated the certificate was stolen "quite some time ago." ®