Paranoid Penguin - Building a Secure Squid Web Proxy, Part II
Squid's Performance Benefits
The Paranoid Penguin is a security column, so naturally, security is our primary focus in dealing with Squid (or it will be, once I've walked you through the basics of getting it up and running). But, you should be aware that Squid is not a security application per se. Squid's main purpose in life is to cache commonly accessed Web and FTP content locally, thereby both reducing Internet bandwidth usage and speeding up end users' download times.
The negative side of this is that Squid doesn't have as rich of a security feature set built in to it as commercial security-oriented Web proxies, such as BlueCoat and Sidewinder. In fact, Squid (years ago) used to ship with a default configuration that allowed completely open access.
The good side is that Squid can be configured, especially along with add-ons like SquidGuard, to provide some of the most important Web proxy security features. And, even if those features are your main reason for deploying Squid, you'll still enjoy the performance benefits of having commonly accessed Web content cached locally by Squid.
Seldom, in the security business, do we enhance end users' experience when we add security controls.
With any luck, at this point, chances are that everything works! Your Squid proxy software is installed, configured to accept only client connections from itself and from hosts on your local network, and it's hard at work proxying your users' connections and caching commonly accessed content. Not a bad day's work!
Not difficult, was it? Like most server applications, Squid's default configuration file is designed to maximize your chances for success, while minimizing the odds of your shiny-new Squid server being hacked. But, also like other server applications, there's certainly more that you can and should do to secure your Squid proxy than the default settings will do for you.
That will be our starting point next month. Among other things, we'll delve much deeper into Squid's Access Control List features to further harden Squid. Until then, be safe!
The Squid home page, where you can obtain the latest source code and binaries for Squid: www.squid-cache.org
The Ubuntu Server Guide's Squid Chapter: https://help.ubuntu.com/8.10/serverguide/C/squid.html
The Squid User's Guide: www.deckle.co.za/squid-users-guide/Main_Page
Mick Bauer (firstname.lastname@example.org) is Network Security Architect for one of the US's largest banks. He is the author of the O'Reilly book Linux Server Security, 2nd edition (formerly called Building Secure Servers With Linux), an occasional presenter at information security conferences and composer of the “Network Engineering Polka”.
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