Cross-site request forgery (CSRF) in Cybersecurity - Step-by-Step Execution

Concept Flow - Cross-site request forgery (CSRF)

User logged into Site A

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User visits malicious Site B

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Site B sends hidden request to Site A

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Browser sends request with User's cookies

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Site A processes request as if from User

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Unintended action happens on Site A

This flow shows how a user logged into one site can be tricked by another site to perform unwanted actions without their knowledge.

Execution Sample

Cybersecurity

User logged in to BankSite
User visits MaliciousSite
MaliciousSite sends hidden form POST to BankSite
Browser sends request with BankSite cookies
BankSite processes request as valid

This example shows how a malicious site can cause a user's browser to send a request to a trusted site using the user's credentials.

Analysis Table

Step	Action	Request Sent?	Cookies Included?	Site Processing	Result
1	User logs into BankSite	No	No	N/A	User authenticated on BankSite
2	User visits MaliciousSite	No	No	N/A	User on MaliciousSite page
3	MaliciousSite creates hidden form targeting BankSite	No	No	N/A	Form ready to submit
4	MaliciousSite auto-submits form	Yes	Yes (BankSite cookies)	BankSite receives request	Request treated as from user
5	BankSite performs action (e.g., transfer money)	N/A	N/A	Action executed	Unintended transaction occurs
6	User unaware of action	N/A	N/A	N/A	Security breach due to CSRF

💡 Process ends after BankSite executes the unintended action triggered by the forged request.

State Tracker

Variable	Start	After Step 2	After Step 4	Final
User Authentication	Logged in	Logged in	Logged in	Logged in
Request Sent	No	No	Yes	Yes
Cookies Included	No	No	Yes	Yes
Site Action	None	None	Unintended action	Unintended action

Key Insights - 3 Insights

Why does the malicious request include the user's cookies even though the user did not submit it?

Because the browser automatically includes cookies for the target site with any request sent to that site, as shown in step 4 of the execution_table.

Why does the trusted site process the malicious request as if it came from the user?

Because the request includes valid authentication cookies, so the site assumes it is a legitimate user action, as seen in step 4 and 5.

Why is the user unaware of the unintended action?

Because the malicious request happens in the background without user interaction, and the user is on a different site, as shown in step 6.

Visual Quiz - 3 Questions

Look at the execution_table at step 4. What is true about the request sent?

A It is sent from the user directly

B It does not include any cookies

C It includes the user's cookies for BankSite

D It is blocked by the browser

💡 Hint

Check the 'Cookies Included?' column at step 4 in the execution_table.

At which step does the BankSite perform the unintended action?

A Step 3

B Step 5

C Step 4

D Step 6

💡 Hint

Look at the 'Site Processing' and 'Result' columns in the execution_table.

If the browser did not send cookies with the request, what would happen?

A The request would be rejected or treated as unauthenticated

B The malicious site would gain access to user data

C The request would still be processed as valid

D The user would be logged out automatically

💡 Hint

Refer to the importance of cookies in the 'Cookies Included?' column in the execution_table.

Concept Snapshot

Cross-site request forgery (CSRF) tricks a logged-in user's browser into sending unwanted requests to a trusted site.
The browser includes authentication cookies automatically.
The trusted site processes the request as if from the user.
This can cause unintended actions like money transfers.
Protection involves verifying requests with tokens or checking origins.

Full Transcript

Cross-site request forgery (CSRF) happens when a user logged into a trusted site visits a malicious site that secretly sends a request to the trusted site. The browser automatically includes the user's authentication cookies with this request. The trusted site processes the request as if it came from the user, causing unintended actions like unauthorized transactions. The user does not realize this because the malicious request happens in the background. Understanding this flow helps in recognizing why CSRF is a security risk and why protections like tokens are necessary.