SQL injection

SQL injection (SQLi) is an attack technique in which attackers exploit a vulnerability in the database query of a web application to inject malicious SQL commands. These commands allow the attacker to gain access to confidential data, manipulate or delete entries and even compromise the entire database system. SQL injection attacks are among the most common and dangerous attacks on web applications because they exploit vulnerabilities in the structure of database queries, often from insecure user input.

How an SQL injection works

SQL injections work by an attacker injecting SQL code directly into the user input fields of a web application that are not sufficiently protected against malicious code. This injected SQL code is then executed by the database system together with the regular query and can enable the following actions:

1. Reading confidential data: Attackers can access sensitive data such as user names, passwords or credit card details that are not normally accessible to the public.
2. Manipulating data: Attackers can use SQL injection to change data records or create new entries in the database. This could include, for example, changing a user’s authorizations.
3. Deletion of data: Attackers may be able to delete records or empty the entire database, causing significant damage to a company or organization.
4. Execution of administration commands: SQL injection can allow attackers to perform administrative actions on the database, such as creating new users with administrator rights.

Types of SQL injection attacks

There are several types of SQL injection attacks, which differ in the approach and the targets of the attack:

1. Simple SQL injection: With this method, SQL code is entered directly into an input field in order to extract or manipulate data. For example, an attacker could enter OR '1'='1' in the login field to gain access.
2. Blind SQL injection: In some cases, the web application does not return specific error messages when there is an SQL injection. In such cases, attackers perform queries to indirectly determine whether certain data exists, for example by making queries “blindly” and watching for other reactions (e.g. whether a page is loaded or an error message is issued).
3. Time-based SQL injection: This variant is based on the fact that the database is forced to slow down by certain commands. This allows the attacker to deduce from reactions and time delays whether a particular query was successful without visible results being displayed.
4. Union-based SQL injection: With this technique, UNION commands are built into the query to combine the data of the original query with the attacker’s data and thus extract additional information.

Risks and consequences of an SQL injection

SQL injection attacks can have significant consequences for organizations and their data integrity. Typical risks include:

• Data theft: SQL injections can give attackers access to sensitive data such as customer data, financial data or other confidential information.
• Loss of data integrity: Attackers can manipulate or delete database entries, which leads to a loss of data integrity and impairs the use of the database.
• Financial damage: The loss of data can mean considerable financial damage for companies, for example through business interruptions, loss of reputation or fines.
• Legal consequences: Data leaks can lead to legal consequences, especially if sensitive customer data has been disclosed.

Protective measures against SQL injection

SQL injection attacks can be prevented by a combination of secure programming standards and security measures:

1. Input validation and cleanup: User input should be strictly validated and sanitized before it is inserted into an SQL query. It is important not to insert user input directly into SQL commands.
2. Prepared statements (parameterized queries): Using prepared statements and parameterized queries is one of the best ways to prevent SQL injections. This technique ensures that input is treated as data and not as code.
3. Stored procedures: Using stored procedures instead of direct SQL statements can also reduce SQL injection risks as they only allow predefined commands.
4. Least Privilege Principle: Database user accounts should only have the minimum required authorizations to perform the required actions. This prevents attackers from accessing the entire system, even if they find a vulnerability.
5. Error handling: Error messages should be designed in such a way that they do not reveal any sensitive information. Blocking detailed error messages prevents attackers from obtaining information about the database structure or potential vulnerabilities.
6. Web Application Firewalls (WAF): WAFs can detect and block SQL injection attacks before they reach the web application. They filter incoming data traffic and search for suspicious patterns.

Reaction to an SQL injection

If an SQL injection attack is detected, companies should take the following steps:

1. Close the security gap: The affected application should be checked immediately and the vulnerability eliminated, for example by implementing prepared statements.
2. Check systems: The database and related systems should be checked for tampering, unauthorized access and data leaks.
3. Change passwords: If access data is affected, passwords should be changed and all affected accounts should be protected.
4. Inform users: If personal data is involved, users should be informed and made aware of potential risks and protective measures.

In summary, SQL injection is a serious security threat that arises from insecure database queries and can have serious consequences for data and system integrity. Preventive measures such as prepared statements, input validation and the correct assignment of authorizations are crucial to effectively ward off SQL injections and ensure the security of the database.

Do you have any questions? Write to us or simply give us a call: +49 212 880 22 962.