This is embarrassing :-[ as I'm a Sysadmin with 6 years experience
then you should know that this is not a threat

this is classed as PUP = not virus / Possible Unwanted Program … usually crap that comes bundled with freeware downloads
avast PUP detection is default off…exept for in boot scan…so if you want PUP detection, turn it on

Malwarebytes and AdwCleaner are good tools to remove this crap with http://malwaretips.com/blogs/smileys-we-love-removal/
also see avast! Browser Cleanup Tool at the bottom of website here http://www.avast.com/store

if you need help removing it, then attach the logs from the guide Asyn gave you