I found out that DuckDuckGo used to set a tracking cookie, even though they claimed they didn't. (!) Back then, I used DuckDuckGo as my default search engine believing I was totally safe. Now I hate them more than Google, at least with Google you know what you're getting yourself into. You can read all about it here: https://archive.is/qntuk I would switch to secure search engines like ixquick, searx or Startpage.