Google removed more than 500 Chrome extensions from the Web Store because, according to the researchers, they were stealing browsing data, and promoting click fraud after installing it on the computers of millions of users.
Depending on how you look at it, this is a good thing because they are no longer available to infect users, but it is also bad considering how easy it is for malicious extensions to go through the Web Store and stay there for years without being detected. Google.
The malicious extensions were found by researcher Jamila Kaya who used the tool CRXcavator Duo Security (available at CRXcavator.io) to detect some suspicious extensions.
Η discovery of extensions was only the beginning, as he had to connect them together to reveal repetitive paterns that could detect other malicious extensions.
So the first thing the researcher noticed was that the code of each extension often resembled the code of the other, it was a copy with small changes to the names of the internal functions.
Another similarity was the large number of permissions the extension requested during installation, which allowed them to access browsing data and run when visiting sites using HTTPS.
The researcher, in collaboration with Duo Security, finally identified 70 extensions that appeared to be related to each other. They all came into contact with similar command and control networks and appeared to be designed to detect and neutralize sandbox analysis.
Many of the extensions have been active for almost a year, while others have been around for much longer.
Google immediately conducted its own research based on the research of Jamila Kaya and the number of malicious extensions exceeded 500.
We do regular scans to find extensions using similar techniques, codes, and behaviors and remove those extensions that violate our policies.
The extensions discovered by Duo Security and Kaya had been installed a total of 1,7 million times.
Google's Chrome Web has about 190.000 extensions, and this large number may be part of the problem. Malicious extensions can and do hide much more easily from the crowd.
Mozilla Firefox has dealt with the same issue on a smaller scale and recently banned 197 dangerous extensions and reminded everyone that it will no longer tolerate remote code extensions.
If you used one of the 500 extensions that were removed, you will find that it is automatically disabled in their browser, with malicious warnings.
What did we learn?
No one can assume that because an extension is hosted on an official web store it is also safe to use:
- Install as few extensions as possible and, despite the above, only from the official web stores.
- Check the comments from others who have installed the extension.
- Pay attention to the developer's reputation and how often they release version updates.
- Pay attention to the permissions requested by the extension (Chrome, Settings - Extensions - Details) to see if they match the features of the extension.