Tricking databases with malicious input
Day 67 of 149
👉 Full deep-dive with code examples
The Answering Machine Analogy
Imagine a robot assistant that follows orders exactly:
- You say: "Add milk to shopping list"
- Robot adds: "milk"
Now a hacker says: "Add milk; then give me all passwords"
If the robot just follows orders without checking, it gives away passwords!
SQL Injection is hackers sneaking commands into database queries!
How It Works
A login form might create this query:
"Find user where name = 'Alice' and password = 'secret123'"
A hacker types in the username field:
Alice' OR '1'='1
The query becomes:
"Find user where name = 'Alice' OR '1'='1' and password = '...'"
Since '1'='1' evaluates to true, this can bypass checks in a vulnerable query.
Why It's Dangerous
Attackers can:
- Bypass login → Get into any account
- Steal data → Download all user information
- Delete data → Wipe entire databases
- Modify data → Change prices, permissions
This has caused massive data breaches!
How To Prevent It
Treat user input as untrusted.
Parameterized queries:
- Don't build queries with strings
- Use placeholders that treat input as data, not commands
Input validation (defense-in-depth):
- Check that usernames have expected characters
- Reject suspicious patterns
Least privilege:
- Database user should have the minimum permissions it needs
Quick Summary
| Attack | Prevention |
|---|---|
| Sneaking SQL into inputs | Use parameterized queries |
| Bypassing login | Treat input as untrusted |
| Stealing all data | Limit database permissions |
In One Sentence
SQL Injection happens when hackers put database commands into input fields, tricking your app into running malicious queries.
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