Linux security tips

Here are some general security tips concerning Linux

• /bin/false can be used as shell to prevent user to login, but other stuff will work


• An asterisk (*) or exclamation mark (!) instead of password in /etc/shadow file means that there is no password and account is locked


• To chroot users and disable ssh (allow sftp only) use rssh
  


• Top 20 OpenSSH Server Best Security Practices


• 20 Linux Server Hardening Security Tips

Kerberos auth for SSH via PAM
auth sufficient pam_unix.so
auth required pam_krb5.so

pwconv - converts passwd file to shadow file

sudo example
User_Alias users = %friends
Cmnd_Alias commands = /bin/test
users ALL = NOPASSWD: commands