In late September; researchers from the security/anti-malware firm Eset discovered the first UEFI (defined) rootkit (defined) being used in the wild (namely being present on computing devices used by the general public in their professional and personal lives).
The APT group known as APT28 (who we discussed before on this blog) has been named as being responsible for this advanced threat being distributed to victim systems located in the Central Europe, Eastern Europe and the Balkans.
Why should this threat be considered important?
While this threat is so far limited to targeting systems in Central Europe, Eastern Europe and the Balkans; it has the potential to set a precedent to dramatically increase the persistence of malware on selected systems. This is due to the fact that to save time malware removal usually involves re-installing the operating system. More advanced users may choose to re-create the MBR/GPT, replace the boot sector and rebuild the BCD. Even more informed users may replace the hard disk to remove the malware. This new threat is significant since all of these steps would not remove it.
Eset researchers discovered that the LoJack anti-theft software which was installed compromised systems was being leveraged to start the attacker’s malware instead by using the Windows registry (defined) to load files with very similar names to that of the legitimate LoJack software. They also located a kernel (defined) driver (defined) being used to write the systems firmware when required. Since this tool was a legitimate tool; it has a valid digital signature. This is significant; otherwise the attacker’s tool would not have worked on a 64 bit Windows system. Should attempts to write to the firmware fail, the malware uses a 4 year old vulnerability CVE-2014-8273 (a race condition (defined)) to bypass the write lock.
Once the firmware has been updated it replaces the original LoJack software files with hijacked versions designed to enable further persistence on the compromised systems, namely a backdoor (defined).
How can I protect myself against this threat?
While it is less likely a threat of this sophistication will become widespread; the steps below will help to defend you against this and similar threats in the future. How this threat establishes an initial foothold on a system was inconclusive by Eset. However exercising caution on the links you click in emails, IMs and social networking should provide some form of prevention. Keeping your system up to date should also prevent a drive by download (defined). However I will detail more specific defensive steps below:
Eset determined that this threat can be prevented from affecting a system by enabling the Secure Boot hardware security feature (if your system has this feature available; most systems manufactured from 2012 onwards do). Any system with a certified Windows 8 or Windows 10 badge on the outside will have Secure Boot enabled with no action required from you. Secure Boot works even better when paired with Intel BootGuard (corporate users are more likely to use/enable this feature).
If the rootkit had affected the system described above it would have then refused to boot due to Secure Boot being enabled. It’s important to clarify that Secure Boot won’t prevent the infection/tampering but it will prevent that tampering from starting the system for use as normal.
Secure Boot was added to Windows 8.0 in 2012 to prevent unsigned components (e.g. rootkits) from affecting a system so early in the boot process that anti-malware software would be unable to detect or prevent that component from obtaining a privileged level of access over the system.
Keeping the UEFI firmware of your system up to date will assist with resolving known vulnerabilities within the firmware. Patching known firmware vulnerabilities makes your system less vulnerable to low level attacks such as this. Please only install UEFI firmware updates from your system vendor. Check the vendor’s website or contact them to determine if you need a UEFI firmware update and how to install it. If possible/available verify the checksum (defined) of the file you download matches the vendors provided checksum. I use the word available above since not all vendors provide checksums of the firmware updates they distribute which would allow you to verify them.
More recent Intel motherboards (defined) are not vulnerable to the race condition by Eset in their paper (more details available here). These modern chipsets feature a Platform Controller Hub (present in Intel’s Series 5 chipsets and later (available circa 2010 onwards).
If you know of a system affected with such a low level threat you may be able to update the UEFI firmware with a known safe version from the vendor but this is not guaranteed to work. Replacing the hardware will be a more reliable alternative.