Lesson 12

Date: 4/12/2017
Basics of Linux Security
Linux System Administration

How systems get compromised

  • Cracked, stollen and sniffed passwords
    john password_file         # John the Ripper
    john -show password_file   # Read the cracked passwds 

    SSH client with a sniffer on a multi-user system:
    reads user name, password and the destination host.

    SSH brute force attack guesses user credentials.

  • Accounts with empty passwords and root privileges
    awk -F: '$2 == "" { print $1, "has no password!" }' /etc/shadow 
    awk -F: '$3 == 0 { print $1, "is a superuser!" }' /etc/passwd 
  • World writable files and directories
    find /dir -xdev -perm /o=w ! \(  -type d -perm /o=t \) ! -type l -print
  • SETUID and SETGID executables
    find /dir -xdev -type f -perm /u=s,g=s -print
  • Trojans
  • Stack overflow attacks on vulnerable services
  • Worms

  • Take me to the Course Website