SQL injection is a technique directed against web applications using an SQL database, which can pose a huge security risk. It involves inserting code into an SQL database, and this attack exploits vulnerabilities in the database or application layer. The main goal of my thesis is to get acquainted with the essence of SQL injection, to understand the various methods of this attack technique and to show ways to defend against it. The work can be divided into these main parts, which I will discuss as follows.In the introductory part of the work I mention the theoretical basis concerning SQL injection issues. The next chapter is focused on individual methods of this technique. The analytical part is devoted to mapping the current state of test subjects, scanning tools, which form the basis for optimal research and testing of individual SQL methods, which are discussed in this part from a practical point of view along with the analysis of commands. In the last part I will implement SQL methods on selected subjects and based on the outputs I will create a universal design solution how to defend against such attacks.

L'internet est devenu un environnement omniprésent dans le monde du travail et du loisir. La popularité sans cesse croissante des applications web ainsi que des services associés entraînent l'exécution de nombreuses transactions critiques, qui soulèvent des questions de sécurité. Du fait de cette croissance, des efforts ont été entrepris durant cette dernière décennie pour rendre les applications web plus sûres. Malgré ces efforts, de récents rapports provenant de l'institut SANS estiment que plus de 60 % des attaques commises sur l'Internet ciblent les applications web en se concentrant sur les vulnérabilités inhérentes aux problèmes de validation, comme le Cross-Site Scripting ou les injections SQL. Dans cette thèse, nous avons conduit deux études de recherche empirique, analysant un grand nombre d'application web vulnérables. Nous avons assemblé une base de données contenant plus de 10.000 rapports de vulnérabilités depuis l'an 2000. Ensuite, nous avons analysé ces données pour déterminer si les développeurs ont pris conscience des problématiques de sécurité web de nos jours, comparé à la période où ces applications émergeaient. Puis nous avons analysé l'étroit lien entre le langage de programmation utilisé pour développer l'application web et le nombre de vulnérabilité reporté. Avec ces résultats empiriques comme base, nous présentons notre solution IPAAS qui aide les développeurs novice en termes de sécurité à écrire des applications sécurisées par défaut. Nous montrons par ailleurs que cette technique améliore de manière probante la sécurité des applications web. / The web has become a backbone of our industry and daily life. The growing popularity of web applications and services and the increasing number of critical transactions being performed, has raised security concerns. For this reason, much effort has been spent over the past decade to make web applications more secure. Despite these efforts, recent data from SANS institute estimates that up to 60% of Internet attacks target web applications and critical vulnerabilities such as cross-site scripting and SQL injection are still very common. In this thesis, we conduct two empirical studies on a large number of web applications vulnerabilities with the aim of gaining deeper insights in how input validation flaws have evolved in the past decade and how these common vulnerabilities can be prevented. Our results suggest that the complexity of the attacks have not changed significantly and that many web problems are still simple in nature. Our studies also show that most SQL injection and a significant number of cross-site scripting vulnerabilities can be prevented using straight-forward validation mechanisms based on common data types. With these empirical results as foundation, we present IPAAS which helps developers that are unaware of security issues to write more secure web applications than they otherwise would do. It includes a novel technique for preventing the exploitation of cross-site scripting and SQL injection vulnerabilities based on automated data type detection of input parameters. We show that this technique results in significant and tangible security improvements for real web applications.