The penny stock market has been through a lot and is still going through some though times. When it comes to scamming, penny stocks are not safe at all.
There're so many people out there who are just promoting some penny stocks that they own. They're doing this as a way to increase their prices so that they can take their profit and move on to the next one.
You have to be very careful when you're buying penny stocks. Specially if you're buying because of good news. Even the news are not 100% trustworthy.
The best way to know that you're trading a stock that's not being pumped is by conducting your own research before you buy.
There's no other way around that. You work hard for your money, you shouldn't lose it in penny stocks without conducting your research.