PCEU Virus

Hi  - a shared home PC with an up to date and fully patched Windows 7 system running NIS 2012 with the very latest updates has 'caught' the PCEU virus.  The virus must have come from a website - not via any mobile media.

 

It wasn't identified or quarantined by NIS 2012 - and the virus managed to circumvent NIS to prevent it working.

 

I solved the problem by cloning a backup copy of the C Drive on to the infected PC.

 

My question is this.  I'm surprised that NIS didn't intercept the virus - and was so easily fooled by PCEU.  Frankly I'm a little disappointed in Norton's performance.

 

What am I missing here?