IPTables for Outbound Connections

IPTables is an application that installed by default with Linux distributions. It works much the same way as Access Control Lists if you are familiar with networking equipment like Cisco Routers.

This guide will give you an overview of how to block incoming connections whilst still allowing established outbound connections.


1. Check if you have any rules in place already. Type $ iptables ­L

Chain INPUT (policy ACCEPT)
target prot opt source destination

Chain FORWARD (policy ACCEPT)
target prot opt source destination

Chain OUTPUT (policy ACCEPT)
target prot opt source destination

2. Allow all connections from localhost

$ iptables ­A INPUT ­i lo ­j ACCEPT

3. Allow only established connections. This is so the response from the external
servers are able to respond $ iptables ­A INPUT ­m conntrack ­­cstate

If there is an issue with that then try $ iptables ­A INPUT ­m state ­­state

4. Finally, we need to add a deny/drop any statement at the end. IPTables does not do this by default like other networking devices

$ iptables ­A INPUT ­j DROP

Other Knowledge Base Topics

Referral Partner
Enquiry Form

send us your details and we will contact you with all the details about our referral partnership

You can also contact us directly:
Tel: 0161 464 6101