Perform Injection Attacks

Perform Injection Attacks: Comprehensive Guide for CEH Exam

Understanding Injection Attacks

Injection attacks are among the most prevalent and dangerous web application vulnerabilities. They occur when untrusted data is sent to an interpreter as part of a command or query, tricking the interpreter into executing unintended commands or accessing unauthorized data.

Why Injection Attacks are Important to Understand:

Injection vulnerabilities consistently rank at the top of security threat lists (including OWASP Top 10) because they:
- Can lead to complete system compromise
- Allow attackers to bypass authentication
- Enable unauthorized data access
- Permit data manipulation or destruction
- Are relatively common in legacy and poorly developed applications

Types of Injection Attacks:

1. SQL Injection (SQLi)
Occurs when malicious SQL code is inserted into database queries. Types include:
- Error-based: Forces database to generate error messages revealing structure
- Union-based: Uses UNION operator to combine results from multiple SELECT statements
- Blind: No visible feedback but can determine truth of statements
- Time-based: Uses time delays to extract information

2. Command Injection
Execution of arbitrary commands on the host operating system via a vulnerable application.

3. LDAP Injection
Manipulation of LDAP queries to access or modify directory information.

4. XML Injection
Tampering with XML input to affect application logic or access unauthorized data.

5. XPath Injection
Modifying XPath queries to bypass authentication or extract data.

6. NoSQL Injection
Similar to SQL injection but targets NoSQL databases like MongoDB.

How Injection Attacks Work:

SQL Injection Example:
Consider a login form with:
- Normal query: SELECT * FROM users WHERE username='input' AND password='input'
- Malicious input: username: admin' --
- Resulting query: SELECT * FROM users WHERE username='admin' -- ' AND password='anything'
The -- makes the database treat everything after it as a comment, effectively removing the password check.

Command Injection Example:
A web application that pings an IP address might use: system("ping " + userInput)
An attacker could input: 127.0.0.1; cat /etc/passwd
This would execute the ping command followed by displaying the password file.

Detection and Testing Methods:

- Input special characters (', ", ;, --, etc.) and observe responses
- Use automated tools like SQLmap, NoSQLmap, or OWASP ZAP
- Look for error messages that reveal database or system information
- Test for blind vulnerabilities using boolean conditions or time delays
- Check all input points (forms, URL parameters, cookies, headers)

Prevention Techniques:

- Use parameterized queries/prepared statements
- Apply input validation (whitelisting preferred over blacklisting)
- Implement proper error handling that doesn't leak system details
- Apply the principle of least privilege for database accounts
- Use ORM (Object-Relational Mapping) frameworks correctly
- Regularly update and patch systems
- Employ Web Application Firewalls (WAFs)

Exam Tips: Answering Questions on Injection Attacks

Key Concepts to Master:
- Understand the syntax differences between various injection types
- Know common payloads for different injection scenarios
- Recognize vulnerable code patterns
- Be familiar with detection tools and methodologies
- Know prevention best practices

Question Approaches:

For scenario-based questions:
1. Identify the technology in use (SQL, LDAP, OS command, etc.)
2. Determine the input method and context
3. Consider what the attacker is trying to achieve
4. Select the most appropriate payload or technique

For prevention questions:
1. Parameterized queries/prepared statements are almost always preferred over escaping
2. Defense in depth is better than single-layer protection
3. Input validation should complement other protections, not replace them

For detection questions:
1. Focus on response analysis and pattern recognition
2. Remember that automated tools have limitations
3. Consider both active and passive detection methods

Common Exam Traps:
- Confusing different injection types and their specific syntax
- Selecting only one protection method when multiple are needed
- Focusing on finding vulnerabilities but forgetting exploitation limitations
- Overlooking the business impact of injection vulnerabilities

Remember that the CEH exam often tests not just your knowledge of how to perform attacks, but also how to identify, mitigate, and prevent them in an enterprise environment.