S0221 Umbreon

A Linux rootkit that provides backdoor access and hides from defenders.

Techniques Used

Domain	ID	Name	Use
enterprise	T1059	Command and Scripting Interpreter	-
enterprise	T1059.003	Windows Command Shell	Umbreon provides access using both standard facilities like SSH and additional access using its backdoor Espeon, providing a reverse shell upon receipt of a special packet¹
enterprise	T1095	Non-Application Layer Protocol	Umbreon provides access to the system via SSH or any other protocol that uses PAM to authenticate.¹
enterprise	T1014	Rootkit	Umbreon hides from defenders by hooking libc function calls, hiding artifacts that would reveal its presence, such as the user account it creates to provide access and undermining strace, a tool often used to identify malware.¹
enterprise	T1205	Traffic Signaling	Umbreon provides additional access using its backdoor Espeon, providing a reverse shell upon receipt of a special packet.¹
enterprise	T1078	Valid Accounts	-
enterprise	T1078.003	Local Accounts	Umbreon creates valid local users to provide access to the system.¹