This is the main web site for my free book, the Secure Programming HOWTO (previously titled Secure Programming for Linux and Unix HOWTO and Secure Programming for Linux HOWTO). This book provides a set of design and implementation guidelines for writing secure programs. Such programs include application programs used as viewers of remote data, web applications (including CGI scripts), network servers, and setuid/setgid programs. This document includes specific guidance for a number of languages, including C, C++, Java, Perl, Python, and Ada95. I give this book away in the hope that future software developers won't repeat past mistakes, resulting in more secure systems.