This article is intended to make RIPE Atlas users, including researchers, aware of ethical issues that could arise when using RIPE Atlas. RIPE Atlas is built on the voluntary contributions of thousands of probe hosts worldwide. On the surface, RIPE Atlas may very well look like a convenient black box that produces useful data in an easy way. But please remember that, as a RIPE Atlas user, you are using someone else's Internet connection to do your measurements. As such, you are effectively a guest of these volunteers.