<h3>Cross-Site Request Forgery (CSRF)</h3>
It is a type of attack that tricks a user into unknowingly performing actions on a web application where they’re authenticated. Here’s a detailed explanation of CSRF, including diagrams and an example to help you write a comprehensive blog post for DailyDev.
<h3>Understanding CSRF</h3>
<h4>What is CSRF?</h4>
Cross-Site Request Forgery (CSRF) is an attack where a malicious actor tricks a user into executing unwanted actions on a web application where they are authenticated. This typically happens because the browser automatically includes the user’s credentials (like cookies) with requests.
<h3>How CSRF Works</h3>
<h4>Basic Concept</h4>
<ol>
<li>User Authentication: The user logs into a web application (e.g., a bank).</li>
<li>Malicious Request: While still logged in, the user visits a malicious website.</li>
<li>Unwanted Action: The malicious website triggers an unwanted action (like transferring money) on the legitimate web application using the user’s credentials.</li>
</ol>
<img src="https://media.daily.dev/image/upload/s--giFDVtBm--/f_auto/v1724590533/ugc/content_b768c66b-52e1-4748-a77b-01260a38cbe8" alt="csrf_exp">
CSRF Visualisation
<h4>Explanation</h4>
Let’s use a simplified diagram to illustrate this:
<ol>
<li>
User Logs In - window1 (google window or any other browser) and tab1
<pre><code>[User] -&gt; [Bank Website] (logged in)
</code></pre>
</li>
<li>
User Visits Malicious Site - on same window1 in tab2
<pre><code>[User] -&gt; [Malicious Website] (contains CSRF attack)
</code></pre>
</li>
<li>
CSRF Attack - malicious code in tab2 website acquires the session storage and sends the request on behalf of you
<pre><code>[Malicious Website] -&gt; [Bank Website]
</code></pre>
Here, the malicious site makes a request to the bank website on behalf of the user without their knowledge.
</li>
</ol>
<h3>Detailed Example</h3>
Let’s say you are logged into your online banking account and have a session cookie that authenticates your requests. Here’s how a CSRF attack might unfold:
<ol>
<li>
Normal Flow:
<ul>
<li>Login: You log into your online banking account.</li>
<li>Session Cookie: The bank website sets a session cookie in your browser to authenticate you.</li>
</ul>
</li>
<li>
Malicious Site:
<ul>
<li>
Crafted Request: An attacker creates a malicious website with a hidden form that performs a money transfer.
<pre><code class="language-html">&lt;html&gt;
&lt;body&gt;
 &lt;form id=&quot;csrfForm&quot; action=&quot;https://bankwebsite.com/transfer&quot; method=&quot;POST&quot;&gt;
 &lt;input type=&quot;hidden&quot; name=&quot;account&quot; value=&quot;attacker_account&quot; /&gt;
 &lt;input type=&quot;hidden&quot; name=&quot;amount&quot; value=&quot;1000&quot; /&gt;
 &lt;/form&gt;
 &lt;script&gt;
 document.getElementById(&#x27;csrfForm&#x27;).submit();
 &lt;/script&gt;
&lt;/body&gt;
&lt;/html&gt;
</code></pre>
</li>
<li>
User Visits Malicious Site: While logged into the bank, you visit the malicious site.
</li>
<li>
Automatic Request: The malicious script automatically submits the form, sending a POST request to the bank’s server with the session cookie.
</li>
</ul>
</li>
<li>
Unwanted Action:
<ul>
<li>Request Sent: The request to transfer money is sent to the bank website, and because your session cookie is included, the bank assumes it’s a legitimate request.</li>
<li>Funds Transferred: Money is transferred to the attacker’s account without your knowledge.</li>
</ul>
</li>
</ol>
<h3>Conclusion</h3>
CSRF attacks exploit the trust that a site has in the user’s browser. By understanding how CSRF works and implementing defenses like anti-CSRF tokens, SameSite cookies, and custom headers, you can significantly reduce the risk of such attacks.
<h3>BONUS:</h3>
Spring Security comes with handling csrf attack with on default no need to add a single line of code. . . we are going to see how springboot handling CSRF attack in next post.
Stay Tuned 🙌
– Balaji Batchu

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CSRF (Cross-Site Request Forgery) is an attack where a malicious actor tricks an authenticated user into performing unwanted actions on a web application. This happens as browsers automatically include user credentials with web requests. The post provides a detailed explanation using diagrams, explaining how such an attack works and emphasizing the importance of implementing defenses like anti-CSRF tokens and SameSite cookies to mitigate risks. It also mentions that Spring Security handles CSRF attack prevention by default.

Spring Security - Cross-Site Request Forgery 🔒