IMac compromised by a virus please help.
Hello,
I have an apple IMac and it seems to have been compromised by a virus. I am not sure how to fix it. I was working on my computer and it suddenly went blank and froze on me. I need help fixing it. My computer has been going blank for the last 4 days and it freezes suddenly. I got an error message saying some program or virus is interfering with the startup. The only way I am able to restore the IMac is by unplugging the chord and restarting it. Sometimes it takes a couple of hours to restart.
Please shed some insights.
Regards.
Michelle
iMac, iOS 8.4