I doubt they are. We've had plenty of people drop in who have demons where they're from. None of them ever quite chalk up to being anywhere near the same.
Physically, the demons alone don't look like much. They're black clouds of smoke, up until they possess a person. It gets tricky when they possess people, too, since you can't just look at any old person and go, "hey, there's a demon!" There's nothing distinguishable about them, unless they personally declare that they're a demon or if their eyes literally go black.
The demons, for the most part, work for Lucifer. They do his bidding, they were created by him, they worship this guy like he's the ultimate religious experience. All in all, they're bad news. It's better to stay as far away from them as you physically can for the most part.
Though, if you're in a jam and if you feel like you gotta deal with them personally, there are a few ways to go about doing that. Know anything about defending yourself against them?
We'd appreciate the help. There's never too much when it comes to what we have to deal with around here on a regular basis.