A Linux backdoor is malware or a hidden access method that lets an attacker keep control of a Linux system after the initial compromise. It may open a covert remote shell, accept commands from a command-and-control server, or create a secret login path that bypasses normal authentication. Because Linux runs many servers, network appliances, containers, and IoT devices, a backdoor can give criminals durable access to valuable infrastructure.
In real attacks, Linux backdoors are used to maintain persistence, move laterally, steal data, and sometimes turn compromised devices into proxies or relay points. They are especially dangerous on internet-facing systems with weak patching or limited monitoring. Defenders look for unusual processes, unexpected outbound connections, altered startup files, suspicious user accounts, and signs of unauthorized command execution. Strong patch management, least-privilege access, file integrity monitoring, and regular log review help detect and remove them.