How do I know if my Sumsang is a counterfeit?

You don't have to. "Sumsang" is definitely fake.

@vish Thanks, captain obvious :)

There is only one way.
Remove the back cover and look at the serial number on the back of the battery. Ok note this down on a paper. Now this is a very important step. Hack into Samsung's product database and search for the serial number. Now this may take a while. Be patient. And if it's not in there I'm afraid it is a fake one.
May the blast be with you!

It's funnier due to the complete lack of a sense of humor that people have.

No it's not, we verified it for you ...
Umm, you're welcome :)

Charge it. If it explodes, you know... If it's real or not.

@samxxx yeah but what with the recent releases and issues, an exploding phone might be real... XD

It's probably a genuine Sumsang, not a fake one.