Botnets typically are coordinated over protocols like HTTP or IRC. However, to make such command and control traffic harder to spot, attackers have occasionally turned to other channels, including normal-looking communication channels like comments on Instagram. Facebook has also been seen in the wild as a method for command and control. The Instagram case linked above used a fairly innocuous-looking comment, and the only way to unravel the command from it was to use a complex regular expression.
I would believe the main responsibility of preventing this abuse of comments usually falls on the security team responsible for identifying and removing the botnet from the infected computers. However, is there any way to prevent this abuse of comments on my own profile/website? I know there are solutions to identify comments that are spam or comments looking for vulnerabilities, but I don't think those comment-filtering solutions would block these C&C comments.