Preventing Web Attacks with Apache [Paperback]

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.

I should start with a disclaimer, I know Ryan Barnett and have followed his work through the years. That said, my responsibility as a reviewer is to help you as the reader decide whether to purchase this book, take the time to leaf through the book with the sample pages or Amazon, or to skip this book. I take that responsibility seriously.

If you have nothing to do with Web servers, you can safely skip this book. If you have operations, security or audit responsibilities for an organization that runs Apache and you do not read this book at least twice you are negligent. Please allow me to explain why I say that.

The book introduces the Center for Internet Security benchmark early on. This group, www.cisecurity.org, does two things very well, they determine to appropriate security configuration for a number of operating systems, devices, and programs and they produce tools to check the configuration. Wouldn't it make sense to know if your web server is configured properly, on average there are about 1,000 web defacements per day.

There are security books that about things and that is OK, but the best security books tell you how to do things. Ryan takes you through the download, installation and configuration of Apache. The "secret sauce" in the book starts in Chapter 5, where you are introduced to what is possible with the security modules for Apache. If you are an auditor, grab your highlighter, mark the tools and configurations and go pay the web admins a visit! Chapter 8 gives you a scenario to bring everything together. For the average reader, this is about as far as you are going to go.

Beyond Chapter 8, you are in advanced material, where Ryan is sharing the results of years of his research. This is for the security person looking for a bit of an edge to help protect their organization, or to do additional research. This is not a book for everyone, but it is a book for everyone running Apache!

Apache is the most common web server out there. It has been heavily built up in functionality by volunteer programmers. Naturally, there are numerous books detailing all that you can do with it. Very versatile. Unfortunately, that is one of the problems! As many commercial websites use Apache, there is a huge incentive for crackers to subvert it in various fashions. Perhaps to get at the back end SQL database. In which might be stored useful information like people's names and credit card data.

Barnett offers inoculation. You can read this book as the sysadmin's manual to installing and running Apache. Where the overriding priority is to bolt down any known weaknesses from the get go.

There is a comprehensive list of attacks. Some might not necessarily be directed against Apache per se, but against any web server. But there are others that might scan for particular versions of Apache or the operating system, if these have bugs that can be exploited. The text suggests possibly providing disinformation. In an earlier, more innocent time, a web server might write its name and version at the bottom of a page that it publishes, for example. Now, you are shown how Apache can suppress this. Better yet, you can tell Apache to pretend to be another web server. A defensive fib that makes the cracker's job a little harder.

Buffer overflows, cross site scripting and SQL injection are possibly the most dangerous attacks explained. For each attack, examples are usually given. Followed by Apache countermeasures. Tangentially, you also get to cast scrutiny at your database and at the entire way your multitier server system is arranged.

The book is a sad but necessary commentary on the times we live in.

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