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Access Control Lists: 6 Key Principles to Keep in Mind
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paul.dittrich
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paul.dittrich,
User Rank: Strategist
1/30/2019 | 3:40:31 PM
Harnessing the power of ACLs
I could not agree more strongly with every point in your column.

It may be fashionable to claim there is no longer a network perimeter but I still strongly favor using the border router as a "garbage filter".

The BOGONs list? - Drop them all.  Invalid TCP flag combinations - Drop.  No Telnet in your environment?  No FTP?  No RDP?  - Block them all at the border router.

As mentioned in the post, the NGFW should take care of the deep packet inspection for only the traffic you potentially want inside your network.  That firewall should see very little traffic except for the known IPs, ports and protocols which are candidates to be allowed all the way in.

And an outbound ACL (a.k.a. egress filtering) is a very powerful weapon against data exfiltration and many types of malware.  You may still have a Trojan but if it can't phone home......


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