For me the biggest source of noise in logs for a small site is the referrer spam. At some point like 12 years ago I enabled webalizer stats with a public link to the stats page. Soon I had to deal with massive amount of bot requests with http referrer pointing to porn and farmacy ads. That has not stopped after the public link was removed and the stats has started to use a public spam database. And the spam is still there after 12 years.