MYRA Linux RAT LD_PRELOAD Rootkit and systemd-userdbd Masquerade via npm

Detects evidence of the MYRA Linux RAT, which uses LD_PRELOAD hijacking via a malicious library located at /usr/local/lib/.libcache.so for persistence or execution flow hijacking. The rule also identifies the malware's practice of masquerading as the 'systemd-userdbd' service, often launched from a Node.js-based environment.