By Martin Stut, 2017-05-02

There are credible claims, outlined in this blog post, that many browser add-ons are sending your full browsing history to analytics companies that may sell this information to anyone willing to pay a certain sum of money. To be sure which browser add-ons are benign, I have used the technique described in this blog post to analyze the traffic generated by certain popular browser add-ons and similar products. The results seem to indicate that the more tracking protection a product claims, the more risk there is that it replaces external tracking with its own tracking.

To keep this article short, I’ll only summarize the results, writing only brief details about the findings. If there is public interest in how I came to the conclusion about one or the other product, please write to me and I may write a public or private summary why I think product X might be doing things users might not want.


Extensions in this list look clean. I did not find suspicious traffic. Of course this doesn’t mean there is no unwanted traffic. I may just have failed to spot the issues…


Extensions in this list clearly send encrypted traffic beyond what is necessary for legitimate operation, or send tracking IDs (by cookie or request data) despite claiming to protect from tracking. To me, encrypted traffic within an already HTTPs encrypted connection indicates the desire to hide something. Hiding content is o.k. for password managers or chat systems, but not for products that should not send anything first place.

Do not use these products if you are visiting confidential members-only websites or if for other reasons would mind your browsing history ending up in the hands of ad-optimizers or anyone else willing to pay for web analytics of other sites.

Avira Browser Plugin

Avira Scout Browser

Cliqz Browser


The “Welcome to Ghostery” page sent tracking requests to, retrieving a piwik script and then sending a tracking message.

IMO promising to stop trackers but at the same time tracking users is not fair play.


Extensions in this list are doing things that look suspicious. They may be benign, but this is hard to tell. I do not recommend using these products with sensitive data, such as health, banking or confidential Intranet sites.


During surfing, apparently all forms encountered (field names, no values) are sent to . This submission includes the domain. So they seem to be mapping innocent web sites for form metadata.

Given the amount of trust needed for a password store, there is too much encrypted traffic compared to the purpose.

Weather Underground

No highly suspicious traffic, although significant amounts of cookies, including, in the weather data requests. Calls to including ruid cookies, which probably enable user tracking.

Browser Safety Systems

Most browsers make use of one of these systems to help protecting you from social engineering attacks and malicious downloads. Each system makes the browser send browsing information to a major pool, which may not be what you want, privacy-wise. You need to make a judgment whether you want to give up some privacy in return for some protection against malicious websites.

Google SafeBrowsing

Turned on by default in Mozilla Firefox.

… works by checking the sites that you visit against lists of reported phishing, unwanted software and malware sites.

When you download an application file, Firefox checks the site hosting it against a list of sites known to contain “malware”. If the site is found on that list, Firefox blocks the file immediately, otherwise it asks Google’s Safe Browsing service if the software is safe by sending it some of the download’s metadata … … including the name, origin, size and a cryptographic hash of the contents.

This means, essentially all downloaded executable files are reported to Google. If you don’t want that, and don’t need the protection, turn it off by going to Firefox > Preferences > Security > “Block dangerous and deceptive content” . Do work from bottom to top, as otherwise some boxes stay ticked but greyed out.

Windows SmartScreen

According to Wikipedia, every website and download is checked against a local list of popular legitimate websites; if the site is not listed, the entire address is sent to Microsoft for further checks. So all visited URLs of confidential Intranet sites, certainly not in the list of popular legitimate websites, will get sent to Microsoft.

You are paying this privacy price in exchange for a high rate (95-99% according to Wikipedia) of protection against social engineered malicious websites. So you need to “choose your poison”.