Linux Server Hardening: SUID Binaries, Sudo Misconfigurations & SSH Hardening

The Danger of Unrestricted SUID and Sudo Permissions

SUID (Set Owner User ID) binaries execute with the privileges of the file owner (typically root). If a binary with GTFOBins escape capabilities (e.g., `find`, `vim`, `bash`) is assigned SUID or sudo rights without password verification, standard users can spawn a root shell in seconds.

Auditing SUID Files with CLI Commands

Execute `find / -perm -4000 -type f 2>/dev/null` across all production servers. Strip unnecessary SUID permissions from all binaries that do not require elevated execution by unprivileged accounts.

SSH Daemon Hardening

Disable root login (`PermitRootLogin no`), enforce ed25519 SSH keys exclusively, disable password authentication, change default listening ports where appropriate, and bind SSH strictly to internal management VPN interfaces.