Starting next year, Microsoft will be a lot stricter when it comes to adware. In a post on the Technet blog, Redmond has announced that it will block advertising programs "that take choice and control away from users." The company's talking about adware that use "man-in-the-middle" (MiTM) techniques, in particular. Those include injecting ads and promotions by proxy, as well as changing DNS settings, without your express consent. They aren't safe, because they could be used to introduce malware into your system, or even to spy on encrypted data and communication.