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Preventing Web Attacks with Apache Review by Richard Bejtlich
A strong mix of Apache security and Web application assessment
I recently received copies of Apache Security (AS) by Ivan Ristic and Preventing Web Attacks with Apache (PWAWA) by Ryan Barnett. I read AS first, then PWAWA. Both are excellent books, but I expect potential readers want to know which is best for them. The following is a radical simplification, and I could honestly recommend readers buy either (or both) books. If you are more concerned with a methodical, comprehensive approach to securing Apache, choose AS. If you want more information on offensive aspects of Web security, choose PWAWA.
Author Ryan Barnett takes a wider look at the world of Web application security than Ivan Ristic. As a result I find their two books very complementary. You'll find coverage of topics in PWAWA that do not appear in AS. For example, Ryan explains how to use the Center for Internet Security Apache Benchmark Scoring Tool to evaluate your httpd.conf file. He uses the Apache Benchmark (ab) application (packaged with Apache) to measure Web server performance characteristics. He uses these tools in before-and-after situations to show how his recommended changes improve the defaults.
I thought PWAWA's coverage of the fundamentals of Web security was not as good as that of AS. That's ok, though, because PWAWA addresses areas not as well covered by AS. For example, PWAWA spends a lot of quality ink on mod_security filters. This is ironic, given that AS author Ivan Ristic coded mod_security! What's impressive about PWAWA's mod_security explanations are the many sample filters. These are developed after discussions of various attack techniques and serve as countermeasures one can implement until a patch is ready.
PWAWA is a mix of defense and offense, with a whole chapter showing how to attack and defend the WebMaven/Buggy Bank learning Web application. Attacks are nice, but showing development of defenses is excellent. PWAWA features some clever ideas too, like snort2modsec.pl and an Open Web Proxy Honeypot. I was not as keen on the inclusion of the Web Application Security Consortium's Web Security "Threat" Classification document. Please search my blog for a thorough discussion of why that guide should be an "attack, vulnerabilities, and exposures" document.
I found few technical nits. It's not correct that a NIDS protects its sniffing interface by "removing [the] IP stack" (p 299). Inline IDS isn't just for honeypots, either. I could have used inline packet rewriting to defend a Web hosting company that had lost control of its IIS customer sites. The customers were compromised and were unwittingly attaching malicious frames in their Web pages, thanks to an intruder.
I was also concerned by the author's statement that upon seeing a Snort Web attack alert, he connects to the Web server via SSH and begins reviewing logs (p 419). Proper network security monitoring wouldn't necessarily require immediate log review, and if log review is needed it should be done via a central log host. Connecting to a potential victim immediately after suspected compromise is a great way to alert the intruder and potentially alter evidence.
Overall, I liked PWAWA. The book is a mix of Apache security and Web application assessment, so if you are more interested in purely securing Apache you might prefer AS. If you want to learn about Web application hacking in general, your best bets are probably Hacking Exposed: Web Applications, 2nd Ed, and Professional Pen Testing for Web Applications. I will read and review those two books shortly.