5 min read

Recently, British Airways was slapped with a $230M fine after attackers stole data from hundreds of thousands of its customers in a massive breach. The fine, the result of a GDPR prosecution, was issued after a 2018 Magecart attack. Attackers were able to insert around 22 lines of code into the airline’s website, allowing them to capture customer credit card numbers and other sensitive pieces of information.

Magecart attacks have largely gone unnoticed within the security world in recent years in spite of the fact that the majority occur at eCommerce companies or other similar businesses that collect credit card information from customers. Magecart has also been responsible for significant damage, theft, and fraud across a variety of industries. According to a 2018 report conducted by RiskIQ and Flashpoint, at least 6,400 websites had been affected by Magecart as of November 2018.

To safeguard against Magecart and protect your organization from web-based threats, there are a few things you should do:

Understand how Magecart attacks happen

There are two approaches hackers take when it comes to Magecart attacks; the first focuses on attacking the main website or application, while the second focuses on exploiting third-party tags. In both cases, the intent is to insert malicious JavaScript which can then skim data from HTML forms and send that data to servers controlled by the attackers.


Users typically enter personal data — whether it’s for authentication, searching for information, or checking out with a credit card — into a website through an HTML

form. Magecart attacks utilize JavaScript to monitor for this kind of sensitive data when

it’s entered into specific form fields, such as a password, social security number, or a credit card number. They then make a copy of it and send the copy to a different server on the internet. 

In the British Airways attack, for example, hackers inserted malicious code into the airline’s baggage claim subdomain, which appears to have been less secure than the main website. This code was referenced on the main website, which when run within the airline’s customers’ browsers, could skim credit card and other personal information.

Get ahead of the confusion that surrounds the attacks

Magecart attacks are very difficult for web teams to identify because they do not take place on the provider’s backend infrastructure, but instead within the visitor’s browser. This means data is transferred directly from the browser to malicious servers, without any interaction with the backend website server — the origin — needing to take place.

As a result, auditing the backend infrastructure and code supporting website on a regular basis won’t stop attacks, because the issue is happening in the user’s browser which traditional auditing won’t detect. 

This means Magecart attacks can only be discovered when the company is alerted to credit card fraud or a client-side code review including all the third-party services takes place. Because of this, there are still many sites online today that hold malicious Magecart JavaScript within their pages leaking sensitive information.

Restrict access to sensitive data

There are a number of things your team can do to prevent Magecart attacks from threatening your website visitors.

First, it’s beneficial if your team limits third-party code on sensitive pages. People tend to add third-party tags all over their websites, but consider if you really need that kind of functionality on high-security pages (like your checkout or login pages). Removing non-essential third-party tags like chat widgets and site surveys from sensitive pages limit your exposure to potentially malicious code. 

Next, you should consider implementing content security policies (CSP). Web teams can build policies that dictate which domains can run code and send data on sensitive pages. While this approach requires ongoing maintenance, it’s one way to prevent malicious hackers from gaining access to visitors’ sensitive information.

Another approach is to adopt a zero-trust strategy. Web teams can look to a third-party security service that allows creating a policy that, by default, blocks access to sensitive data entered in web forms or stored in cookies. Then the team should restrict access to this data to everyone except for a select set of vetted scripts. With these policies in

place, if malicious skimming code does make it onto your site, it won’t be able to access any sensitive information, and alerts will let you know when a vendor’s code has been exploited.

Magecart doesn’t need to destroy your brand. Web skimming attacks can be difficult to detect because they don’t attack core application infrastructure — they focus on the browser where protections are not in place. As such, many brands are confused about how to protect their customers. However, implementing a zero-trust approach, thinking critically about how many third-party tags your website really needs and limiting who is able to run code will help you keep your customer data safe.

Author bio

Peter is the VP of Technology at Instart. Previously, Peter was with Citrix, where he was senior director of product management and marketing for the XenClient product. Prior to that, he held a variety of pre-sales, web development, and IT admin roles, including five years at Marimba working with enterprise change management systems. Peter has a BA in Political Science with a minor in Computer Science from UCSD.

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