Look at your backlinks, if you see a pattern emerging that is something odd or malicious, report it to Google yourself, fighting spammers or negative
SEO is becoming part of your job I guess.
Why do hackers attack sites non-stop, why do referral log automated bots exist, how do you stop them?
Hell there are guys that want to hijack your traffic, take over your server and so on, it is up to you to watch everything, links, IP's hitting your sites, bots hitting your server and so on.