An ad blocker has been detected that is injecting new ads into the browser

ad blocker been detected injecting new ads browser

Imperva experts have discovered the malicious ad blocker AdBlock. Although this browser extension does its job and does block ads, AllBlock injects hidden affiliate links into the browser instead.

The extension is still available in the Chrome Web Store and is positioned as a tool for blocking ads on YouTube and Facebook, including to combat pop-ups and speed up browsing.

Researchers say AllBlock does indeed fight to advertise, but only to implement its own. For example, AllBlock forces legitimate URLs to redirect users to affiliate links controlled by the extension’s developers. This allows fraudsters to make money from advertising themselves or to redirect people to affiliate sites to receive deductions from affiliates.

Specialists discovered the strange AllBlock activity back in August 2021, when they identified a number of previously unknown malicious domains distributing a script to inject ads. The script sent legitimate URLs to the remote server and received a list of domains to redirect in response. If a user clicked on a link modified in this way, they were redirected to another page (usually an affiliate link).

In addition, the script can evade detection, for example, does not catch the eye of large Russian search engines, clears the debug console every 100 ms and actively detects Firebug variables.

After examining the AllBlock blocker in more detail, the Imperva team discovered this script (bg.js) that injects the code into each new tab opened in the browser. To inject a malicious script, the extension connects to a URL on, which returns the script in base64, after which it will be decoded and embedded into the page. At the same time, the developers of the extension even added several harmless objects and variables to the malicious code fragment, trying to hide its malicious functions

How AllBlock is advertised and distributed is not yet clear, but Imperva experts believe that scammers may use other extensions in this campaign. For example, they managed to find some evidence that the same IP addresses and domains link this extension to the malicious Pbot campaign, which has been active since at least 2018.

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