SQLiGoT: Detecting SQL injection attacks using graph of tokens and SVM

SQL injection attacks have been predominant on web databases since the last 15 years. Exploiting input validation flaws, attackers inject SQL code through the front-end of websites and steal data from the back-end databases. Detection of SQL injection attacks has been a challenging problem due to extreme heterogeneity of the attack vectors. In this paper, we present a novel approach to detect injection attacks by modeling SQL queries as graph of tokens and using the centrality measure of nodes to train a Support Vector Machine (SVM). We explore different methods of creating token graphs and propose alternative designs of the system comprising of single and multiple SVMs. The system is designed to work at the database firewall layer and can protect multiple web applications in a shared hosting scenario. Though we focus primarily on web applications developed with PHP and MySQL, the approach can be easily ported to other platforms. The experimental results demonstrate that this technique can effectively identify malicious SQL queries with negligible performance overhead.