Kaspersky promises security and data protection. However, a data leak allowed third parties to spy on users while they were surfing the web. For years.
A strange discovery on my office computer led me to unearth an astonishing data leak caused by Kaspersky’s antivirus software. Originally, I had installed the software in order to experience the promised added value during everyday use. We, journalists at c’t magazine, regularly test antivirus software, and this was part of a test for our c’t issue 3/2019.
The following weeks and months seemed to offer little excitement – the Kaspersky software worked essentially as well or as badly as Windows Defender. One day, however, I made a strange discovery. I looked at the HTML source code of an arbitrary website and came across the following line of code:
Obviously, an external JavaScript script named main.js was being loaded from a Kaspersky domain. This is not uncommon, since a website nowadays hardly works without external JavaScript resources. However, when I checked the HTML source of other websites displayed in my browser, I found the strange code on each and every page. Without exception, even on the website of my bank, a script from Kaspersky was introduced. So I had an inkling that the Kaspersky software might have something to do with it.