Performance Objective

At the conclusion of the course the student will be able to:

  1. Identify the five most popular data base engines.
  2. Identify two ways that data base engines can differ.
  3. Identify what SQL injection is.
  4. Identify one tool used in PHP to prevent SQL injection.
  5. Identify an organization that teaches about SQL injection.
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Many modern breaches involve databases. We regularly hear about leaks, vulnerable software, and companies who were not following best practices being hit by such a basic hack. Why? What kind of software is being written that includes SQLi vulnerabilities?

A Small List from 2017 -

  1. WordPress Plugins (300,000+ sites)
  2. Illinois State Board Of Elections (Voter Registration System)
  3. Joomla
  4. Web Forums (65000+ Accounts at an Airsoft site alone)
  5. Moodle
  6. McAfee ePolicy Admin Console
  7. US Election Commision Voting Machines

Also check out the wall of shame for more interesting mistakes.


The most popular SQL servers are -

  1. Oracle
  2. MySQL or MariaDB
  3. Microsoft SQL Server
  4. PostgreSQL
  5. IBM DB2

It is very important that you figure out which server is being employed by your target. This should be one of your top goals as you begin the process of executing an attack. Each server will have both minor as well as major differences in syntax and function that will require specific changes in behavior when attempting to exploit flaws. We must also keep in mind some of the differences in license we can run into as well.


SQL injection is a code technique that can be used to cause unwanted behavior in your application. Some of the results of an SQL injection attack include the following -

  1. Destruction of data.
  2. Breach of privacy.
  3. Access control loss.


Avoiding SQL injection is often possible through the use of one or more methods. Each of these methods will require some effort by the programmer working on the application. It should be understood however that many modern frameworks now provide many of these tools as baked in tools. While it is possible to simply pass a raw SQL query without any form of parameterization, it can now require more effort to do it wrong than right.

A cheat sheet is available for anyone interested in learning more about SQL injection. The Open Web Application Security Project is a great tool for learning about cyber security.

Parameterized Queries

A prepared statement with parameterized queries allows the developer to bind a variable. You must first define your SQL code and then you pass in each parameter later. Even if a user were to try to inject ‘userid = tom; or 1=1’ then the query will see a literal string and look instead for the userid of ‘tom’ or ‘1=1’ as a string. It prevents interpretation of input by the database.

PHP Example of Prepared Statement

// prepare and bind
$stmt = $conn->prepare("INSERT INTO MyGuests (firstname, lastname, email) VALUES (?, ?, ?)");
$stmt->bind_param("sss", $firstname, $lastname, $email);

// set parameters and execute
$firstname = "John";
$lastname = "Doe";
$email = "";

Stored Procedures

A stored procedue is an alternative to prepared statements. A user would store an SQL query in the database, call it, and then pass a variable to it before execution. You are setting the SQL query and not making any changes beyond passing a variable.

White List Input Validation

You can white list certain variables like table names or column names, however, if you are using a white list, there is a good chance you should be able to rewrite your code to not need it. You should not be allowing a user to pass a table name, column name, or other database related information from input.


Escaping content, such as replacing all single quotes with double quotes is an iffy proposition and not recommended as a replacement for prepared statements. You should perform some form of input validation, provide a whitelist of acceptable content, and never use string concantentation. This is not replacement for prepared statements or stored procedures.

Least Privilege

Do not allow your application to connect to your database using the root user. Least privilege includes user rights, resource permissions, and privilege elevation mitigation. You should carefully map out your application and understand what rights and tools are necessary and then only white list those aspects of the application. If your middleware only needs access to a single database, then it should only have access to that single database and no more.

You must pay attention to what is used and what is necessary to prevent a system or aspect of the application possibly becoming a vector to intrusion.

Code Review

Review your code. Peer review, automted or tool assisted review, or pair programming are all viable methods to get more eyes on code. Each of these options increases the development time, but when properly implemented, will greatly reduce the amount of time spent on trying to fix code after it has already been deployed.


Automated testing is far superior to manual inspection.

Tools include N-Stealth, Web Vulnerability Scanner, SPI Web Inspect, and Nikto. These are just a handful of tools that can be used to automate the testing of your application. It is also possible to create a testing path that is used in conjunction with continous integration to automatically monitor for vulnerabilities every time you push the application an update.

  1. N-Stealth
  2. Nikto
  3. Web Inspect
  4. CI


  1. Oracle, MySQL, Microsoft SQL, PostreSQL, and IBM DB2 are the five most popular data base engines.

  2. Query Syntax and Stored Function/Procs Language Choice are two ways they differ.

  3. SQL Injection is the result of running unvalidated SQL queries through an application by the use of exploits or with the help of poorly designed interfaces.

  4. Prepared statements or parameterized queries can help defend against SQL injection.

  5. OWASP ( Open Web Application Security Project )


Breaches happen to the best prepared. It is inevitable that someone could potentially find some kind of vulnerability in your application or project. It is not an excuse or a blessing that allows a developer to ignore best practices. You must develop your software in the most secure method possible while using all the tools available to mitigate the threat. You should not ignore security just because it is an up hill battle.

Final Recommendations

  1. Use Linux!

  2. Review code and foster a positive environment for improvement. No bruised egos.

  3. Set metrics and perform testing. Example: Reduce calls for service by 12%.

  4. Encourage all team members to think security.

  5. Perform automated security reviews. Consider creating a CI toolset.


  1. SQL - Structured Query Language. A language for interacting with relational databases

  2. MariaDB - An open source tool that fulfills the same functionality of MySQL.

  3. CI - Continous Integration. The practice of integrating code into a shared repository several times a day.