Q: How can I get rid of this virus/malware?

Quit Safari from the Apple > Force Quit menu. Relaunch Safari from the Dock icon while holding down the Shift key.

AdwareMedic removes all known adware from your Mac. http://www.adwaremedic.com/index.php

Reading this might also be helpful.

Mac Malware Guide: How do I protect myself?  http://www.thesafemac.com/mmg-defense/

Please read How to install adware.

Safari/Browsers - Eliminating browser redirects and advertisements

Safari/Browsers - Eliminating browser redirects and advertisements (2)

Try running this program and then copy and paste the output in a reply. The program was created by Etresoft, a frequent contributor.  Please use copy and paste as screen shots can be hard to read. On the screen with Options, please open Options and check the bottom 2 boxes before running. Click “Share Report” button in the toolbar, select “Copy to Clipboard” and then paste into a reply. This will show what is running on your computer. No personal information is shown.
  

Etrecheck – System Information