"Masons" are professional stone cutters. You mean Freemasons? No.
First of all, they are a lodge, not a religion. And their members include people of all different kinds of religions. They are as much of a "Satanic organization" as the Elks lodge, a college fraternity, or the 4H Club.
There are lots of bogus conspiracy theories out there, and they're just that: bogus conspiracy theories. It's just a bunch of unfounded urban legends. A lot of them were propagated by disgruntled ex-members. You can most likely FIND to a Masonic lodge chapter in your home town, go there, and see for yourself.
It's true that lodges often have members-only secrets, but trust me, you'd be sorely disappointed if you found out what they were. They're things like "This is our secret handshake" or "The lion in our crest represents the strength of brotherhood", etc. The point in these is simply to add to the ceremonial experience. Humans simply like ceremonies and symbols, with or without a religious context.