An innocent-looking Blu-ray disc can be used by malicious actors to get a foothold in a targeted network, a researcher has warned.
According to Stephen Tomkinson of the NCC Group, both hardware and software Blu-ray players are plagued by vulnerabilities that can be leveraged to execute arbitrary files stored on the disc.
The advanced features provided by Blu-ray discs, such as dynamic menus and Web access, are built using BD-J (Blu-ray Disc Java). The specification is used to create interfaces and embedded applications called Xlets. Xlets are similar to Java applets, but they are specially designed for digital TV environments.
Xlets run in a Java VM and they use the SecurityManager class to implement security policies. Tomkinson noted that, in general, these security policies prevent discs from accessing elements outside of the virtual file system and prevent interaction with the underlying operating system.
In his tests, Tomkinson targeted PowerDVD, a popular Blu-ray player application developed by CyberLink. The researcher has found a way to disable the SecurityManager developed by CyberLink and gain access to methods that can be used to launch arbitrary executable files stored on the disc.
On systems where PowerDVD is installed, Blu-ray discs are automatically played with the application, which enables attackers to bypass autorun attack mitigations in Windows, the expert said.
CyberLink says it has been made aware of the potential vulnerability, but the company doesn't appear too concerned.
"Because of the AACS (Advanced Access Content System) protection and BDA (Blu-Ray Disc Association) verification layers on all commercial Blu-Ray movies, as well as the additional levels of security provided by CyberLink, including verification of such protection and approval, it’s a highly implausible risk," CyberLink told SecurityWeek.
"The only way that a person with malicious intent could add malware or a virus to Blu-Ray movies is unrealistic. It would require them to manually create a new disc image that bypasses PowerDVD verification, spend the money to buy physical discs, burn each of them individually and use illicit distribution channels in hope of eventually reaching consumers," the company added. "Regardless, we are taking any potential risk to our customers’ security very seriously, have already identified a solution and will implement it shortly."
As for physical Blu-ray players, the researcher used an exploit previously developed by Malcolm Stagg to get a shell on the device. From there, Tomkinson managed to come up with a way to execute arbitrary files located on the disc.
Both software and physical players can be targeted with a single disc, the researcher said. An attacker can create a disc that detects the player type and executes a malicious file specific to that platform. In order to avoid raising suspicion, a legitimate video file can be played right after the malicious files are launched.
“[The malicious] executables could be used by an attacker to provide a tunnel into the target network or to exfiltrate sensitive files, for example,” Tomkinson explained in a blog post.
The researcher has pointed out that in the case of physical Blu-ray players, an attacker needs to ensure that the device doesn’t go to sleep after the victim has stopped viewing the video. This can be achieved by intercepting the power off request and by switching off the power LED in order to avoid raising suspicion.
In an attack targeted at a corporate network, if the player is configured for Wi-Fi access, malicious actors can easily obtain Wi-Fi settings because the information is stored on the device unencrypted.
The NCC Group says it’s working with affected vendors to get the vulnerabilities fixed, but “with varying degrees of success.” Until the vulnerabilities are addressed, Tomkinson advises users not to utilize discs from untrusted sources, and disable the autoplay feature. In the case of hardware players, they should not be connected to the network or the Internet unless necessary.
Using removable media to distribute malware is not unheard of. The Equation Group, an entity that is believed to have ties to the NSA, reportedly replaced CD-ROMs sent out by the organizers of a scientific conference with ones containing malware.
*Updated with statement from CyberLink