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linux firewall implementation

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by manoj_u_99

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i have implemented a linux based firewall kernel version 2.2.12.using ipchains.
could u tell me which are the ports and services to be blocked for maximum protection of our lan network.the lan spans around 600 computers.
thank u manojkumar_u@hotmail.com

5 replies

by mckaytech

Because there are 65,535 ports, the usual approach is to block all ports and services and then specifically enable only those that are necessary for a business purpose.

The most common port to allow through is 80 (http for web browsing). Close behind that is 25 (smtp for e-mail). Beyond that, you want to only open ports where there is a specific request for a specific reason.

paul

by kevin anderson

On your external NIC, block everything.

Portscan the Linux box, and if anything shows up, shut it down.

No external ports need to be open for people to go out.

Kev.

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