If you are getting notifications from PreferredBit, then your Mac is infected with adware. PreferredBit is adware for Mac.
PreferredBit changes setting in your Mac. First, PreferredBit installs a browser extension in your browser. Then, after PreferredBit hijacks your browser, it modifies settings in the browser. For example, it changes the default home page, modifies search results, and displays unwanted pop-ups in your browser.