Ebury is an SSH backdoor targeting Linux operating systems. Attackers require root-level access, which allows them to replace SSH binaries (ssh, sshd, ssh-add, etc) or modify a shared library used by OpenSSH (libkeyutils).[1][2]

ID: S0377
Platforms: Linux
Contributors: Marc-Etienne M.Léveillé, ESET
Version: 1.2
Created: 19 April 2019
Last Modified: 21 October 2020

Techniques Used

Domain ID Name Use
Enterprise T1071 .004 Application Layer Protocol: DNS

Ebury has used DNS requests over UDP port 53 for C2.[1]

Enterprise T1554 Compromise Client Software Binary

Ebury has been embedded into modified OpenSSH binaries to gain persistent access to SSH credential information.[1]

Enterprise T1132 .001 Data Encoding: Standard Encoding

Ebury has encoded C2 traffic in hexadecimal format.[1]

Enterprise T1568 .002 Dynamic Resolution: Domain Generation Algorithms

Ebury has used a DGA to generate a domain name for C2.[1]

Enterprise T1573 .001 Encrypted Channel: Symmetric Cryptography

Ebury has encrypted C2 traffic using the client IP address, then encoded it as a hexadecimal string.[1]

Enterprise T1562 .002 Impair Defenses: Disable Windows Event Logging

Ebury has disabled logging when the backdoor is used.[1]

Enterprise T1556 Modify Authentication Process

Ebury can intercept private keys using a trojanized ssh-add function.[1]

Enterprise T1027 Obfuscated Files or Information

Ebury has obfuscated its strings with a simple XOR encryption with a static key.[1]

Enterprise T1553 .002 Subvert Trust Controls: Code Signing

Ebury has installed a self-signed RPM package mimicking the original system package on RPM based systems.[1]

Enterprise T1552 .004 Unsecured Credentials: Private Keys

Ebury has intercepted unencrypted private keys as well as private key pass-phrases.[1]