The rule 'Code Injection by ld.so Preload' is designed to detect unauthorized modifications to the ld.so preload configuration file, which is critical in Linux environments. This file can be exploited by malicious actors to force the dynamic linker to load malicious shared libraries into processes, enabling persistence and privilege escalation attacks. The detection mechanism leverages keyword searches for the presence of the file `/etc/ld.so.preload`, indicating potential misuse or manipulation for injecting unwanted code. The significance of monitoring this file stems from its ability to compromise the integrity of system processes if modified, making it an essential aspect of system security. Given the potential danger posed by code injection techniques, this rule provides a high-level alert to security analysts when the specified conditions are met, enhancing the overall threat detection capabilities for Linux systems.