secure a linux server (one day mayb)

mana tau satu hari bleh wat server sndiri so aku post note utk secure server. kot2 nanti xde la susah2 nak cari .. dia ckp use lsof atau apa2 tools 

command utk find out connection port mana pc aku guna


ns003:~# lsof -i
COMMAND PID USER FD TYPE DEVICE SIZE NODE NAME
named 17829 root 4u IPv6 12689530 UDP *:34327
named 17829 root 6u IPv4 12689531 UDP *:34329
named 17829 root 20u IPv4 12689526 UDP ns003.unternet.net:domain
named 17829 root 21u IPv4 12689527 TCP ns003.unternet.net:domain (LISTEN)
named 17829 root 22u IPv4 12689528 UDP 209.40.205.146:domain
named 17829 root 23u IPv4 12689529 TCP 209.40.205.146:domain (LISTEN)
lighttpd 17841 www-data 4u IPv4 12689564 TCP *:www (LISTEN)
sshd 17860 root 3u IPv6 12689580 TCP *:ssh (LISTEN)
sshd 17880 root 3u IPv6 12689629 TCP *:8899 (LISTEN)
sshd 30435 root 4u IPv6 74368139 TCP 209.40.205.146:8899->dsl-189-130-12-20.prod-infinitum.com.mx:3262 (ESTABLISHED)


Don't allow root logins on your primary sshd port 22 (set PermitRootLogin to "no"); many automated tools run brute-force attacks on that. Set up a secondary port for root access that only works by shared keys, disallowing passwords: Copy the sshd_config file to root_sshd_config, and change the following items in the new file:

• Port from 22 to some other number, say 8899 (don't use this! make up your own!)
• PermitRootLogin from "no" (you were supposed to set it to "no" for port 22, remember?) to "yes"
• AllowUsers root add this line, or if it exists, change it to allow only root logins on this port
• ChallengeResponseAuthentication no uncomment this line if it's commented out, and make sure it says "no" instead of "yes"

test command ni

• 
  
  sshd -D -f /etc/ssh/root_sshd_config
  and see if it works correctly -- try logging in from another computer (you must have already set up shared-key authentication between the two computers) using:
  
  ssh -p8899 root@my.remote.server
  and if so, control-C at the above (sshd) command to stop the sshd daemon, then add this to the end of /etc/inittab:
  
  rssh:2345:respawn:sshd -D -f /etc/ssh/root_sshd_config
  
• Restart the init task: # init q This will run your "root ssh daemon" as a background task, automatically restarting it in case of failure.