Symbiote: A New, Nearly-Impossible-to-Detect Linux Threat

Ars Technica reports:
Researchers have unearthed a discovery that doesn't occur all that often in the realm of malware: a mature, never-before-seen Linux backdoor that uses novel evasion techniques to conceal its presence on infected servers, in some cases even with a forensic investigation.

On Thursday, researchers and the BlackBerry Threat Research & Intelligence Team said that the previously undetected backdoor combines high levels of access with the ability to scrub any sign of infection from the file system, system processes, and network traffic. Dubbed Symbiote, it targets financial institutions in Brazil and was first detected in November.

Researchers for Intezer and BlackBerry wrote:

'What makes Symbiote different from other Linux malware that we usually come across, is that it needs to infect other running processes to inflict damage on infected machines. Instead of being a standalone executable file that is run to infect a machine, it is a shared object (SO) library that is loaded into all running processes using LD_PRELOAD (T1574.006), and parasitically infects the machine. Once it has infected all the running processes, it provides the threat actor with rootkit functionality, the ability to harvest credentials, and remote access capability....'

So far, there's no evidence of infections in the wild, only malware samples found online. It's unlikely this malware is widely active at the moment, but with stealth this robust, how can we be sure?


'When hooked functions are called, the malware first dynamically loads libc and calls the original function...' according to Blackberry's blog post. 'If the calling application is trying to access a file or folder under /proc, the malware scrubs the output from process names that are on its list.... If the calling application is not trying to access something under /proc, the malware instead scrubs the result from a file list....

'Symbiote also has functionality to hide network activity on the infected machine.'

Read more of this story at Slashdot.