1. A computer-implemented method comprising: analyzing characteristics of a website to determine whether the website represents a potential source of spam content, wherein the analyzing comprises: generating a characterizing signature of a webpage containing a content item, wherein the characterizing signature is derived from formatting data of the webpage; obtaining an occurrence count for the generated characterizing signature; and when the obtained occurrence count is greater than a threshold count, identifying the content item as spam content; and flagging the content item of the website as spam content.