Within Viber - probably a scam:

We congratulate you!

Your phone number (+XX XXXXXXXXX) won in the daily lottery for free!

>>> Your prize - Apple iPhone 6 Plus (128Gb) <<<

To get the prize, download and install the free application below and wait for further instructions.

http://goo.gl/9X1zCa

http://goo.gl/cU9Vxy

http://goo.gl/cJIMzF