SQL injection via network in Computer Networks - Mini Project: Build & Apply

Understanding SQL Injection via Network

📖 Scenario: You are a network security analyst learning about how attackers can exploit SQL injection vulnerabilities through network requests. Understanding this helps protect systems from unauthorized data access.

🎯 Goal: Build a simple step-by-step explanation of how SQL injection can happen via network communication, using a clear example of a vulnerable query and how an attacker might exploit it.

📋 What You'll Learn

Create a sample SQL query string vulnerable to injection

Define a malicious input string that an attacker might send over the network

Show how the malicious input modifies the original query

Explain the final impact of the injection on the database query

💡 Why This Matters

🌍 Real World

Network security analysts use this knowledge to identify and prevent attacks that exploit SQL injection vulnerabilities over network connections.

💼 Career

Understanding SQL injection is essential for cybersecurity roles, database administrators, and developers to protect sensitive data and maintain secure systems.

1

Create a vulnerable SQL query string

Create a variable called query that holds the string "SELECT * FROM users WHERE username = '" concatenated with a variable user_input and then concatenated with "';". For now, set user_input to "admin".

Computer Networks

user_input = "admin"
query = "SELECT * FROM users WHERE username = '" + user_input + "';"
# Your code here

Hint

Think of how a simple SQL query looks when searching for a username.

2

Define a malicious input simulating an attack

Change the value of user_input to the string "admin' OR '1'='1" to simulate an attacker trying to manipulate the query.

Computer Networks

user_input = "admin' OR '1'='1"
# Your code here

Hint

This input tries to trick the database into returning all users by adding a condition that is always true.

3

Show how the malicious input changes the query

Create a variable called injected_query that combines the string "SELECT * FROM users WHERE username = '", the user_input, and "';" to show the full query after injection.

Computer Networks

injected_query = "SELECT * FROM users WHERE username = '" + user_input + "';"
# Your code here

Hint

Show the full SQL query string that the database will receive after the attacker's input.

4

Explain the impact of the SQL injection

Create a variable called impact and assign it the string "The injected query returns all users because the condition '1'='1' is always true." to describe the effect of the injection.

Computer Networks

impact = "The injected query returns all users because the condition '1'='1' is always true."
# Your code here

Hint

Explain in simple words what happens when the database runs the injected query.

Practice

1. What is SQL injection via network in simple terms?

easy

A. A way to backup database data remotely

B. A method to speed up database queries over the network

C. An attack where harmful commands are sent to a database through a network connection

D. A network protocol for secure database communication

Solution

1. Step 1: Understand the meaning of SQL injection

   SQL injection means sending harmful commands to a database to manipulate or steal data.

2. Step 2: Connect SQL injection with network

   When these harmful commands are sent through a network connection, it is called SQL injection via network.

3. Final Answer:

   An attack where harmful commands are sent to a database through a network connection -> Option C

4. Quick Check:

   SQL injection via network = harmful commands sent over network [OK]

Hint: Think: harmful commands sent through network to database [OK]

Common Mistakes:

• Confusing SQL injection with normal database queries
• Thinking it is a backup or speed method
• Mixing it up with network security protocols

2. Which of the following is a correct way to prevent SQL injection via network?

easy

A. Use input validation and parameterized queries

B. Send raw SQL commands directly over the network

C. Disable network connections to the database

D. Allow all user inputs without checks

Solution

1. Step 1: Identify safe practices against SQL injection

   Input validation checks user data, and parameterized queries separate data from commands, preventing injection.

2. Step 2: Evaluate other options

   Sending raw commands or allowing unchecked inputs increases risk; disabling network is impractical.

3. Final Answer:

   Use input validation and parameterized queries -> Option A

4. Quick Check:

   Safe coding = input validation + parameterized queries [OK]

Hint: Prevent injection by validating inputs and using safe queries [OK]

Common Mistakes:

• Thinking disabling network is practical
• Believing raw SQL commands are safe
• Ignoring input validation importance

3. Consider this SQL query sent over a network: SELECT * FROM users WHERE username = '' OR '1'='1';. What is the likely result?

medium

A. Causes the database to crash

B. Returns no users because of syntax error

C. Returns only users with empty username

D. Returns all users because the condition is always true

Solution

1. Step 1: Analyze the SQL condition

   The condition username = '' OR '1'='1' means either username is empty or '1' equals '1'. Since '1'='1' is always true, the whole condition is true for all rows.

2. Step 2: Understand query effect

   Because the WHERE clause is always true, the query returns all users from the table.

3. Final Answer:

   Returns all users because the condition is always true -> Option D

4. Quick Check:

   Always true condition returns all rows [OK]

Hint: Look for always true conditions like '1'='1' [OK]

Common Mistakes:

• Assuming syntax error due to quotes
• Thinking it returns no rows
• Believing it crashes the database

4. A developer wrote this query to get user info: "SELECT * FROM users WHERE id = " + user_input; sent over network. What is the main problem?

medium

A. It concatenates user input directly, risking SQL injection

B. It uses prepared statements safely

C. It uses parameterized queries correctly

D. It encrypts user input before sending

Solution

1. Step 1: Examine how user input is used

   The query concatenates user input directly into the SQL string, which can allow attackers to insert harmful commands.

2. Step 2: Identify risk of SQL injection

   Direct concatenation without validation or parameterization is a common cause of SQL injection vulnerabilities.

3. Final Answer:

   It concatenates user input directly, risking SQL injection -> Option A

4. Quick Check:

   Direct input concatenation = injection risk [OK]

Hint: Avoid direct string concatenation with user input [OK]

Common Mistakes:

• Thinking concatenation is safe
• Confusing with parameterized queries
• Assuming encryption is done automatically

5. You receive a network log showing this suspicious query: SELECT * FROM accounts WHERE user = 'admin'--' AND password = 'anything'; What does the -- do in this SQL injection attempt?

hard

A. Encrypts the password part of the query

B. Comments out the rest of the query, bypassing password check

C. Ends the SQL statement safely

D. Causes a syntax error and stops execution

Solution

1. Step 1: Understand the role of -- in SQL

   The -- sequence starts a comment in SQL, ignoring everything after it on the same line.

2. Step 2: Analyze the effect on the query

   By commenting out the password check, the attacker bypasses authentication, gaining access as 'admin'.

3. Final Answer:

   Comments out the rest of the query, bypassing password check -> Option B

4. Quick Check:

   -- = comment to skip code [OK]

Hint: Remember -- starts a comment in SQL [OK]

Common Mistakes:

• Thinking -- encrypts or ends query safely
• Assuming it causes syntax error
• Not realizing it bypasses checks