Can the Firefox Plugin, Greasemonkey, be detected by web servers?

My friend's account for some Facebo开发者_运维问答ok game was suspended on the grounds that he had Greasemonkey installed on his browser. He is asked to uninstall Greasemonkey and account has been restored. My question is how can a web server detect a client side plugin presence?

I assume that Greasemonkey or Greasemonkey scripts operate on the client side only so it would not be possible for the server to detect it.

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If you send a lot of informations to the Facebook Server from the greasemonkey script, facebook can analyse that this requests are not send from a normal user. greasemonkey scripts to fill out any forms are ok, but scripts which are sending a lot of requests to a server are detectable.

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The server could detect it if advertises itself in the form of a user-agent string, or if the server makes use of it's own browser plugin, that plugin could be used to detect the presence of other plugins.

However, if "your friend" was using greasemonkey to cheat, then the game probably detects the fact that he was cheating (e.g. submitting an inhuman number of requests per minute, say) and guessed it was greasemonkey.

The moral of the story is: don't cheat.