The set-uid Bit

• ls -l /usr/bin/passwd

  • -r-s--x--x 1 root root 22312 Sep 25 1999 /usr/bin/passwd

• SUID (set user ID, octal 4000, or s)

• SGID (set group ID, octal 2000, or S)

• If SUID/SGID set for a directory, users belonging to the authorized group can alter only their own files in that directory.

• Partitions can be mounted "no setuid" (/, /var, /usr, /tmp, /home, /opt).

Notes: