My scrum master said, 'I would optimize your work hours.' He's monitoring how much time every one spends on browsing non-productive webs like devRant. How can I fight back? :(

Use SSH tunnelling to proxy your connection in firefox, so all they will see will be encrypted packages to a single host (that will be pretty much unknown for them). I am a Dreamhost customer and they offer that in the cheapest plan. If you have a hosting company, check if they allow that as well.

Micromanaging rarely works.

I don't think he knows what scrum master is supposed to do. Send him instructions or something.

Give him some articles from likedin about productivity for developers, moat say we need to distract ourselves. Also reach your deadlines and goals AND browse irrelevant stuff to show you are alfa.

Your scrum master is a douche and doesn't know anything about managing devs.

Here - send him a poop emoji by a temporary email, every half an hour or an hour. :)