Hi and wlecome to imore. Let's see if we can help you.
Did you update it to iOS 7.1.2?
If so, remember the iPhone 4 is nearly four years old now, with four year old hardware and iOS 7 is the last iteration of iOS that the phone will support. You're likely to get sluggish behaviour on the older hardware for a start.
And I expect you were being glib with your remark about Apple sending a virus to your phone as we all know that's just a stupid thing for Apple to do.
Firstly though, try a soft reset by holding down the Power button and Home button until you see a white screen with the Apple logo on it, then let go of both buttons and let the phone start up normally. See if that helps your battery drain and overheating.