Virus not detected by Norton

I have been using Norton for some time on my computer and my daughter's.  Recently my daughter's computer has been infected by a virus that was not detected by norton.  I don't know what the name of the virus is but it changed her Internet Explorer home page to postarticles.net.  Everytime she re-booted her computer, it would re-set the home page to this site.  After doing some research on line, it appears this is a virus spread through windows messenger.  I am currently running malwarebytes to see if I can get ride of the virus. 

I am very disappointed though that Norton did not detect and remove this virus.  Norton isn't cheap and I would have thought this is exactly the sort of threat I expect it to protect us from.  Apparently the virus we are having problems with has been around for a while and is common so I would have thought Norton would have a definition for it.