Malvertising is the term given to the abuse of ad networks to serve malicious adverts on legitimate websites that scam visitors by displaying popup ads or direct them to malicious websites hosting phishing forms or exploit code to silently deliver malware. Many website owners place third-party advertising blocks on their websites to increase revenue. While the ad networks have controls in place to prevent abuse, cybercriminals often succeed in bypassing those security measures.

web protection

One cybercriminal group has been particularly active over the past year and has been conducting attacks on a massive scale. Researchers at Confiant have been tracking the activity of the group – known as eGobbler – and report that the group delivered fake adverts on 500 million user sessions in Europe and the United States in the past week alone. The campaigns are on a truly massive scale. One of the latest campaigns, conducted between August 1 and September 23 involved around 1.16 billion ad impressions.

Typically, the criminals behind these campaigns target mobile users as the security protections on their devices are nowhere near as robust as on desktop computers; however, this campaign has targeted desktop users on Windows, Linux, and macOS.

Several content delivery networks have been used to serve the malicious adverts, which redirect users to websites that exploit two browser vulnerabilities to deliver their malicious payloads. The first is a bug in the Chrome browser – CVE-2019-5840 – which was patched by Google in June. The second is a zero-day vulnerability in WebKit, the browser engine used by old Chrome versions and the Safari web browser. The bug has already been patched for Safari, but currently Google has not patched Chrome. Since the latest browser engine used by Chrome is based on WebKit, later versions are also affected.

While sandboxing features protect advertising iframes, the zero-day vulnerability has allowed the group to break out of the iframes and display malicious code to visitors and perform redirects.

This cybercriminal group is atypical of most groups that use malvertising to deliver malware. The group is highly skilled and capable of finding bugs in the source code of browsers and conducts campaigns on a massive scale. The group poses a significant threat to internet users although there are steps that can be taken to reduce the likelihood of an attack.

Personal users can harden their defenses by using ad-blockers and ensuring they keep their browsers updated. Businesses similarly need to ensure browsers are updated and block these malicious adverts using a web filtering solution.

In addition to blocking malicious adverts, a web filter can be configured to block the download of malicious files and prevent employees from visiting phishing websites and other malicious websites. A web filter can also be used by businesses to enforce acceptable internet usage policies.

TitanHQ has developed a powerful DNS-based web filtering solution for SMBs and MSPs – WebTitan – that provides protection against malvertising and other types of web-based attacks. The solution is easy to use and can be implemented in just a few minutes. No technical skill is required.

Considering the level of protection provided by WebTitan, you are likely to be surprised at how little the solution costs. To find out more, to arrange a product demonstration, or to set up free trial of the full solution, give the TitanHQ sales team a call.