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Moein Hosseini
Asked: 2012-02-03 11:22:29 +0800 CST

How to filter some protocols on all ports

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Under CentOS, how can I filter traffic by protocol rather than by port?

For example, I would like to filter ftp traffic regardless of the port being used in order to prevent users on the network from using ftp.

I would like to drop the packet, not reject them.

centos networking port filter

1 Answers

  1. Best Answer

    What you are asking about is typically called an "application layer" firewall or "layer 7" firewall because it operates at layer 7 of the OSI model. A layer 7 filter operates by inspecting all packets passing through the firewall in order to identify the protocol in use.

    There is a layer 7 classifier available for use with Netfilter, the Linux firewall implementation. It doesn't appear to be an especially active project, but neither is completely stale -- the last update on the main page appears to be from January of last year.

    I don't have any personal experience with this module.

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