Unix Security Assessment
Unix assessment centers on file permissions, accounts, services, and privilege. Understand the permission model: owner/group/other with read/write/execute, and the special bits - setuid (run as owner), setgid (run as group / inherit directory group), and sticky bit (restrict deletion in shared directories). Know that a setuid-root binary is a high-value target and that world-writable files and directories are findings. Understand umask and how it shapes default permissions.
Know the account and authentication files: /etc/passwd (world-readable account info, shell, UID), /etc/shadow (hashed passwords, restricted), and sudo configuration (/etc/sudoers) for delegated privilege. Understand service management and exposure via listening sockets, and the principle of running services as unprivileged users. Recognize SSH configuration weaknesses (permit root login, password auth) and key file permissions.
Trap: questions often confuse setuid with setgid, or assume /etc/passwd still holds password hashes - modern systems keep them in /etc/shadow. Another trap is treating a world-readable file as harmless when it contains secrets.
Rule of thumb: when reviewing permissions, look for setuid-root binaries, world-writable paths in the executable search path, and secrets readable by all. Any of these can enable privilege escalation.