[Tucker]

What are some common red-flags that webmasters should look for when analyzing their traffic. By red-flags, I mean signs that say something fishy or problematic is going on with your traffic, such as massive hits from a single IP.

[Dana]

Great question.
To me, anything sudden would be a cause for concern if it's for no reason, ie: not creating something new and suddenly your traffic goes bonkers.
I would also worry about multiple hits from the same IP or region. I can't think of anything else off the top of my head but look forward to other members' insights :)

[tianlei]

I'm not so sure those are a bad thing, especially the second one. Many colleges and universities have the same IP address for everyone living on campus. And you could just have an article that was picked up by someone who started sharing the link.

[willyoumind]

Those things that I mostly concern for a website is the security and the click bombers! If your site has been targeted by the hackers or spammers, especially the google adsense click bombers, then you should report the issue to Big G asap!