it is not wise to block port 8291, because the exploitable service is on http port 80 tcp.
The worm uses port 8291 to identify possible victims (when it can connect to port 8291 it assumes there is a MikroTik router on that address), then attacks it on port 80 and some other ports that people may likely have set as an alternative for HTTP access to the router (8080 etc).
So blocking port 8291 effectively blocks the worm in its current version, while not destroying the useful port 80. Of course experience with earlier events like this shows that such a worm typically evolves and may skip the port 8291 scan later, rendering this block ineffective.
For now, I have blocked access to port 8291 from addresses outside AMPRnet on our gateway. Of course this restriction will be lifted when/if this worm stops operation.
It appears to be controlled via a peer-to-peer network and it looks like it is a version of an existing worm that has been active on network cameras/recorders, routers from other manufacturers, etc, all running embedded Linux.
Rob