Be Aware of A SCAM involving fradulent checks!

I am a recent victim of a scam here, so I want to warn everyone about it!
The scammers would send you a check beforehand, and you would be able to deposit the money in your account. The problem is that THE CHECK GETS RETURNED AFTER MANY DAYS! (Apparently banks don't actually check the money at the deposit time, so it looks like the check is valid. I didn't know it, as a foreigner not used to checks.) In my case it was worse, they pretended making a mistake and sent me a lot more money, then rushed me to send them back the extra money. The police told me it's a very popular scam now.