About

"The cancer that is killing /b/" is a common phrase used to refer to whatever and whomever one would blame for the perceived decline in the quality of content on 4chan's /b/. Common culprits often labeled as cancer include, but are not limited to furries, griefers, moralfags, and most commonly newfags. A newfag is nothing more than a noob in Chanspeak.

Origin

The catchphrase's has an arguable origin, but it has been noted that it started being use after 4chan's notoriety grew massive prevalence through the internet.