Old and New OpenSSH Backdoors Threaten Linux Servers

OpenSSH, a suite of networking software that allows secure communications over an unsecured network, is the most common tool for system administrators to manage rented Linux servers. And given that over one-third of public-facing internet servers run Linux, it shouldn’t come as a surprise that threat actors would exploit OpenSSH’s popularity to gain control of them.

Nearly five years ago, ESET researchers helped to disrupt a 25 thousand-strong botnet of Linux machines that were saddled with an OpenSSH-based backdoor and credential stealer named Ebury. The attackers wielding it first performed a check if other SSH backdoors are present at the targeted system before deploying the malware.

Book a demo today to see GlobalDots is action.

Optimize cloud costs, control spend, and automate for deeper insights and efficiency.

Book a demo today to see GlobalDots is action.

This spurred the researchers to search for and analyze these type of (server-side OpenSSH) backdoors.

They found that there is a wide spectrum of complexity in backdoor implementation, starting from off-the-shelf malware to obfuscated samples and network protocols, but that all of them are the result of modifying and recompiling the original portable OpenSSH source used on Linux.

Also, that there are multiple code bases for the various backdoors, but that most of them share similar basic features (e.g., hardcoded credentials to activate a backdoor mode, credential stealing).

All of the collected samples copy the stolen credentials to a local file, even though attackers then must log back onto the compromised machine to retrieve the file. But some of the malware families are also capable of pushing the credentials on the network.

A cartoonish puffer fish wearing sunglasses and a tie,holding a briefcase labeled 'TOP SECRET'.
Image Source

Read more: Help Net Security 

Latest Articles

What is an API Security Audit?

 In January 2024, a misconfigured API exposed 650,000 private messages. These included passwords and internal communications. No exploit chain. No zero-day. Just a public-facing endpoint with no authentication. This wasn’t an isolated incident. From T-Mobile and Twitter (now X) to Kronos Research and the US Treasury, attackers have consistently used APIs as entry points. They […]

Ganesh The Awesome
26th June, 2025
The Ultimate API Security Checklist for 2025

APIs are now the top attack vector in enterprise apps. In 2024 alone, breaches tied to APIs cost an average of $4.88 million, and that number is rising fast. Attackers exploit gaps in API authentication, input validation, and outdated endpoints to compromise systems. Legacy controls no longer suffice, and the OWASP API Top 10 outlines […]

Ganesh The Awesome
26th June, 2025
10 API Security Best Practices for 2025

APIs are the backbone of today’s interconnected software. They power everything from mobile apps and SaaS platforms to internal microservices and partner integrations. But their rapid growth has left many security teams flat-footed. In 2025, many attackers prefer to exploit API misconfigurations hiding in plain sight. What used to be fringe cases (token leakage, zombie […]

Ganesh The Awesome
23rd June, 2025
API Security in 2025: Practical Assessment & Modern Protection Strategies

APIs are no longer an edge case. In 2025, they’re a core requirement for maintaining trust, compliance, and operational continuity. As organizations build more API-driven systems—from customer apps to internal microservices—the exposure risk compounds. And quickly, too. Even mature security teams are finding that traditional tools can’t keep pace with the volume, velocity, and nuance […]

Ganesh The Awesome
23rd June, 2025

Unlock Your Cloud Potential

Schedule a call with our experts. Discover new technology and get recommendations to improve your performance.

    GlobalDots' industry expertise proactively addressed structural inefficiencies that would have otherwise hindered our success. Their laser focus is why I would recommend them as a partner to other companies

    Marco Kaiser
    Marco Kaiser

    CTO

    Legal Services

    GlobalDots has helped us to scale up our innovative capabilities, and in significantly improving our service provided to our clients

    Antonio Ostuni
    Antonio Ostuni

    CIO

    IT Services

    It's common for 3rd parties to work with a limited number of vendors - GlobalDots and its multi-vendor approach is different. Thanks to GlobalDots vendors umbrella, the hybrid-cloud migration was exceedingly smooth

    Motti Shpirer
    Motti Shpirer

    VP of Infrastructure & Technology

    Advertising Services