Yes, it is really possible, and lost 0,08BTC that way, only 16$ at that time, but much more now. However, since I placed a password to my wallet (yeah, was pretty stupid to don't put one : I thought I'd have to enter it each time I would get into my wallet 
), never had any problem 
!
), never had any problem !That is not a big amount of money, but is never fun to get hacked and lost your money. If someone has access to your PC or your smartphone with a virus or malware, for sure he can access and transfer the fund to another bitcoin adresse.
Always a good idea to implement the basic security into your wallet