Linux Script custom

Need to write a simple shell script ( Ubuntu/CentOS) that is ran using crontab, idea is to scan for number of connections per ip, if it exceeds specified limit, run command to block that IP in our firewall. Functions: 1. run netstat -atun | awk '{print $5}' | cut -d: -f1 | sed -e '/^$/d' |sort | uniq -c | sort -n 2. scan number of connections and IP addresses sample output: 2 [login to view URL] 2 [login to view URL] 3 [login to view URL] 5 [login to view URL] 5 [login to view URL] 5 [login to view URL] 6 [login to view URL] 6 [login to view URL] 8 [login to view URL] 9 0.0.0.0 10 [login to view URL] 12 [login to view URL] 22 [login to view URL] 22 [login to view URL] 24 [login to view URL] 24 [login to view URL] 60 [login to view URL] 370 [login to view URL] 450 [login to view URL] Threshhold limit in conf is for ex 200 that means the last 2 ips should be blocked using command: csf -d [login to view URL] csf -d 450 175.137.180 use sendmail to email this event (only if block was done) Must work without bugs/crashing/memory leaks etc, at end of script it must be terminated.