Threat Signal Report

Syslogk: Linux Rootkit with Hidden Backdoor Payload

description-logo Description

FortiGuard Labs is aware of a report that a new rootkit for Linux that appears to be still in development was discovered. Namaed "Syslogk", the rootkit is based on Adore-Ng, an old open-source kernel rootkit for Linux. Syslogk is hides directories containing malicious files and does not load the hidden Rekoobe backdoor malware until specifically-crafted magic packets are received.



Why is this Significant?

This is significant because "Syslogk" is a Linux rootkit that is in development as such it may be used in real attacks in near future. The rootkit contains a new variant of Rekoobe backdoor that will be launched only upon receiving specifically crafted magic packets from the threat actor.



What is Syslogk?

Syslogk is a Linux rootkit that is reportedly based on an old open-source Linux kernel rootkit called "Adore-Ng".


Syslogk rootkit is installed as kernel modules in the affected system and intercepts legitimate Linux commands in order to hide its files, folders, or processes. It can hide directories containing the malicious files dropped on the compromised machine, hides processes and network traffic, and remotely starts or stop payloads on demand. The rootkit is also capable of inspecting all TCP traffic. The rootkit also loads hidden Rekoobe backdoor only when it receives specifically-crafted magic packets from the threat actor.



What is Rekoobe?

Rekoobe is a Linux backdoor that is reportedly based on TinySHell, an open-source Unix backdoor. Rekoobe refers to its Command-and Control (C2) server and performs malicious activities based on remote commands it receives.



What is the Status of Coverage?

FortiGuard Labs provides the following coverage against Syslogk rootkit:


Linux/Rootkit_Agent.BY!tr


FortiGuard Labs provides the following coverage against Rekoobe backdoor:

Linux/Rekoobe.B

Linux/Rekoobe.B!tr

Linux/Rekoobe.B!tr.bdr

Linux/Rekoobe.D!tr

Linux/Rekoobe.F!tr

Linux/Rekoobe.N!tr

Linux/Agnt.A!tr

Linux/Agent.B!tr

Linux/Agent.BX!tr.bdr

Linux/Agent.DL!tr

Linux/Agent.JO!tr

Linux/Agent.LF!tr

W32/Rekoobe.F!tr

W32/Multi.MIBSUN!tr.bdr

ELF/Rosta.487B.fam!tr.bdr

Adware/Agent

Adware/Rekoobe

PossibleThreat


Definitions

Traffic Light Protocol

Color When Should it Be used? How may it be shared?

TLP: RED

Not for disclosure, restricted to participants only.
Sources may use TLP:RED when information cannot be effectively acted upon by additional parties, and could lead to impacts on a party's privacy, reputation, or operations if misused. Recipients may not share TLP:RED information with any parties outside of the specific exchange, meeting, or conversation in which it was originally disclosed. In the context of a meeting, for example, TLP:RED information is limited to those present at the meeting. In most circumstances, TLP:RED should be exchanged verbally or in person.

TLP: AMBER

Limited disclosure, restricted to participants’ organizations.
Sources may use TLP:AMBER when information requires support to be effectively acted upon, yet carries risks to privacy, reputation, or operations if shared outside of the organizations involved. Recipients may only share TLP:AMBER information with members of their own organization, and with clients or customers who need to know the information to protect themselves or prevent further harm. Sources are at liberty to specify additional intended limits of the sharing: these must be adhered to.

TLP: GREEN

Limited disclosure, restricted to the community.
Sources may use TLP:GREEN when information is useful for the awareness of all participating organizations as well as with peers within the broader community or sector. Recipients may share TLP:GREEN information with peers and partner organizations within their sector or community, but not via publicly accessible channels. Information in this category can be circulated widely within a particular community. TLP:GREEN information may not be released outside of the community.

TLP: WHITE

Disclosure is not limited.
Sources may use TLP:WHITE when information carries minimal or no foreseeable risk of misuse, in accordance with applicable rules and procedures for public release. Subject to standard copyright rules, TLP:WHITE information may be distributed without restriction.