This shouldn't be attributed to just Norton though, point this out, as many AV's have specific malicious code that it cannot detect. (As the second stanza in the quoted text points out). It's been like this for years though, which is why I've always said that you cannot rely 100% on any AV, you still have to be self-aware.
Best thing to do would be to sandbox that file in question and really see what it is doing on your system or trying to do. If you are curious enough.