Handy Linux network stat commands
Netstat can be used to do a lot of things, I usually use it to keep track of how many connections there are to my server. These are my two most used commands
Show the number of connections on your http port
netstat -nta | grep :80 | wc -l
List the top10 ips using the highest number of connections to your server
netstat -atnp -A inet | awk -F " " '{print $5} ' | awk -F ":" '{print $1}' | sort | uniq -c | sort -nr | head -10
If there are some bad offenders in the list, you can ban their ip by using IP tables.
Ban:
sudo iptables -A INPUT -s <IPHERE> -j DROP
Unban:
sudo iptables -D INPUT -s <IPHERE> -j DROP
These are temporary bans, if you want to save them you will need to save the IP tables and restart the IP table service. This is for rhel, fedora and centOS.
sudo service iptables save
sudo service iptables restart