How Does SQL Injection Work and How Can It Be Prevented?

What is SQL injection and its security threat?

SQL injection is a serious database security vulnerability, which occurs when external content is unexpectedly inserted into the SQL query string to change its grammar. Whether it is malicious or accidental errors, this injecting content may modify the query results, so as to grant unauthorized access rights, and even modify sensitive data.

The mechanism injected by SQL

SQL injected vulnerabilities was generated because the attacker deliberately entered the value they knew that they would be embedded in the SQL string. By carefully designing these inputs, the attacker can manipulate the query results, bypass the access limit, retrieve unauthorized information, or perform malicious operations. Consider the following PHP example:

If the attacker sets password = xyzzy and id = account_id, the generated SQL query becomes:

<code class="language-php">$password = $_POST['password'];
$id = $_POST['id'];
$sql = "UPDATE Accounts SET PASSWORD = '$password' WHERE account_id = $id";</code>

The application does not know. The intention of the attacker is to set the password of all accounts, not just their own account. This vulnerability allows attackers to invade multiple accounts.

Vulnerability points and preventive measures

<code class="language-sql">UPDATE Accounts SET PASSWORD = 'xyzzy' WHERE account_id = account_id</code>

SQL injection occurs when the dynamic content of the trusted dynamics that is not appropriately verify is integrated into the SQL string. To prevent injection attacks, developers should use query parameters instead of directly embedding the user into the SQL string. By using parameterized queries, the input value is effectively isolated from SQL syntax, thereby reducing the risk of injection vulnerabilities.

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