Build them carefully and maintain them rigorously, and ACLs will remain a productive piece of your security infrastructure for generations of hardware to come.

In an industry of constant, rapid change, an old-school security tool remains an effective piece of an overall security. Access Control Lists (ACLs) that specify precise rules for destinations and protocols allowed or forbidden, are the foundation of firewalls. And while firewalls have advanced to use analysis of packet contents and behavior, ACLs have not gone away.

There are a number of reasons why ACLs endure. The first, and most important, is that they work. ACLs are straight-forward, conceptually simple ways to limit traffic to and from known (or suspected) malicious addresses and to clear traffic to and from addresses known to be acceptable. Next, they play well with others. As Twitter user Frank Barton (@fbarton) wrote in response to a question about ACLs, "…much less cpu intensive than stateful and deep-packet. But…like Ogres, and onions…use layers. If you can block traffic at ACL, then pass remaining to “NGFW” [next-generation firewall] the fw [firewall] has less traffic to inspect."

As with all security measures, though, how an ACL is deployed will have a major impact on its effectiveness. Of course, precisely how the ACL is programmed will vary from manufacturer to manufacturer, and component to component, but there are key considerations that are true regardless of which device is hosting the ACL. Let's take a look at the principles to keep in mind to make ACLs an effective (and efficient) part of the overall security infrastructure.

(Image: photon_photo — stock.adobe.com)

About the Author(s)

Curtis Franklin, Principal Analyst, Omdia

Curtis Franklin Jr. is Principal Analyst at Omdia, focusing on enterprise security management. Previously, he was senior editor of Dark Reading, editor of Light Reading's Security Now, and executive editor, technology, at InformationWeek, where he was also executive producer of InformationWeek's online radio and podcast episodes

Curtis has been writing about technologies and products in computing and networking since the early 1980s. He has been on staff and contributed to technology-industry publications including BYTE, ComputerWorld, CEO, Enterprise Efficiency, ChannelWeb, Network Computing, InfoWorld, PCWorld, Dark Reading, and ITWorld.com on subjects ranging from mobile enterprise computing to enterprise security and wireless networking.

Curtis is the author of thousands of articles, the co-author of five books, and has been a frequent speaker at computer and networking industry conferences across North America and Europe. His most recent books, Cloud Computing: Technologies and Strategies of the Ubiquitous Data Center, and Securing the Cloud: Security Strategies for the Ubiquitous Data Center, with co-author Brian Chee, are published by Taylor and Francis.

When he's not writing, Curtis is a painter, photographer, cook, and multi-instrumentalist musician. He is active in running, amateur radio (KG4GWA), the MakerFX maker space in Orlando, FL, and is a certified Florida Master Naturalist.

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