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ModSecurity 2.5

You're reading from   ModSecurity 2.5 Prevent web application hacking with this easy to use guide

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Product type Paperback
Published in Nov 2009
Publisher Packt
ISBN-13 9781847194749
Length 280 pages
Edition 1st Edition
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Toc

Table of Contents (17) Chapters Close

ModSecurity 2.5
Credits
About the Author
About the Reviewers
1. Preface
1. Installation and Configuration FREE CHAPTER 2. Writing Rules 3. Performance 4. Audit Logging 5. Virtual Patching 6. Blocking Common Attacks 7. Chroot Jails 8. REMO 9. Protecting a Web Application Directives and Variables Regular Expressions Index

An introduction to regular expressions


Regular expressions are an important part of writing ModSecurity rules. That is why this section contains a short introduction to them and why the book also has an appendix that describes them in more detail.

Regular expressions are a very powerful tool when it comes to string matching. They are used to identify a string of interest, and are useful for many different tasks, such as searching through large text files for a given pattern, or, as used in ModSecurity, to define patterns which should trigger a rule match.

Programming languages such as Perl come with regular expression support built right into the syntax of the language (in fact, the PCRE library that was mentioned in the previous chapter that is used by Apache and ModSecurity is a re-implementation of the regular expression engine used in Perl). Even Java's String class has the matches() method which returns true if the string matches the given regular expression.

Regular expressions are so...

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