How A Cross Site Request Forgery Can Cause Damage To Your Computer And Your Finances

Most computer users tend to trust the software that they use on an everyday basis.

The one piece of software that 90% of the people who own a computer use everyday is their browser.

It doesn’t matter if it is Internet Explorer, Firefox, Opera, or Chrome, these are the tools that people use to surf the web.

Sometimes blind trust in your favorite tool is not the smartest thing in the world.

It can lead you to be unaware of some weaknesses in the tool.

Cross Site Request Forgery

This is what attackers that use a cross site request forgery vector hope to accomplish.

They take the trust that a user has in their browser and turn it against them.

A cross site request forgery works by taking over the user’s browser to submit commands to web site for exploit purposes.

This is able to be done because of the browser’s ability to save your information from a previous visit to a web site.

Web site owners know that a person does not necessarily like to log in every time that they visit a web site.

Or sometimes a web site wants to remember a specific link that you clicked on while you were visiting.

To do this the site will download a cookie onto your computer without your knowledge.

This cookie will have the previous settings of when you visited the site before and you will not have to fill out anything.

An attacker that uses a cross site request forgery is able to use this feature and turn it to their advantage.

For the attack to work, the cookie still has to be valid.

False Linkage

If it is, then the attacker can set a trap by getting a person to click on a specially crafted link.

The link can either be a text link, image link, or even link in a flash based movie.

To the average person the link will look normal.

But to a person that is able to understand the code they will see that the link has extra variables that it shouldn’t.

The link will lead you to the previous site that you visited where the cookie is still valid.

The link will then have variables in it that are known to issue certain commands to that particular web site.

Since your cookie is still valid, the site thinks that the command is authorized by you and will commence to following the order.

If the site targeted is a bank then this means that a hacker can clean your account out and the transfer of funds will seem legitimate to the bank.

All of this from just a simple click of a link.

This form of attack is not an easy one to pull off and requires a lot of work by the attacker for it to work.

This is why you will not see this sort of attack in the wild that often.

It takes homework of not only the site that you want to get the data out of but also the person that you want to attack.

The attack is mainly used against companies and big money targets.

It is rarely effective against the average person.

When executed well, a cross site request forgery attack can leave you in bad shape when it comes to your finances.

If you have any kind of notoriety or own a company, this is an attack that you will want to look out for.

About Lee Munson

Lee's non-technical background allows him to write about internet security in a clear way that is understandable to both IT professionals and people just like you who need simple answers to your security questions.


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