Topic: Help for Block all ports!!!

[Ariel]

in what way block all ports one range ip specific and permit ports 21,25,80,110 only other range ip specific?.
Thank for helpme

[Nathan Fowler]

iptables or ipchains?

[Ariel]

I  tried with /sbin/iptables -A FORWARD -p TCP --dport 1863 -j REJECT
and dont worked, can you send me an example; and if there is any command to block all ports.
Thanks.

[Mario Kerecki]

Hi Ariel,

I have added this script to my sme5.6 server to drop unwanted/unecessary ports on the firewall:

#!/bin/bash
# The following rules drop inbound connections to ports: 110,143,113
# they are not needed for this environment as all access is through  
  ssh and https.
# last line drops pings to the firewall's external interface
#
iptables -I INPUT -i eth1 -p tcp --dport 110 -j DROP
iptables -I INPUT -i eth1 -p tcp --dport 143 -j DROP
iptables -I INPUT -i eth1 -p tcp --dport 113 -j DROP
iptables -I INPUT -i eth1 -p icmp --icmp-type 8 -j DROP

Login as root. Create a file called "dropextra" with the above contents and any other ports you want dropped using the template, make it executable with :

[root@sme5.6 root]# chmod +x dropextra

Assuming your Internet ethernet interface is eth1 (default) you can adjust this for any additional ports/protocols. If you would like it to take effect on reboot and assuming you created the file in the root home directory just do this:

[root@sme5.6 root]# echo "/root/dropextra" >> /etc/rc.d/rc.local

Cheers
-m

[%sig%]

[Mario Kerecki]

Ariel,

Here is a scan of my firewall from the outside to verify that everything worked (real hostnames altered):

[root@otherhost root]# nmap -P0 -sS sme56.somewhere.net

Starting nmap V. 3.00 ( www.insecure.org/nmap/ )
Interesting ports on sme56.somewhere.net:
(The 1596 ports scanned but not shown below are in state: filtered)
Port       State       Service
25/tcp     open        smtp
80/tcp     open        http
443/tcp    open        https

This output is after activating the rules in my previous email. Let me know if you have any further questions.

-m