Homepage removed as a threat

This morning when opening DuckDuckgo it changed to a page from Norton saying my Symantic product has reset your home page after encountering a threat.  I contacted DuckDuckGo and they suggested contacting Norton....

this is the URL: http://us.norton.com/security_response/f...zzzzzz      (I changed and truncated at the end to disable)         Although it looks legit is it?

PS... I changed it back to DuckDuckGo and it seems to be working, but what did this happen? Was there a real threat or what?