I have recently setup a new tor exit node but since about an hour of setting it up it has been almost maxed out with spam.

https://metrics.torproject.org/rs.html#details/4AFECB973C2268D5074D8DEDAF0BDB604C89ED50

How can I combat it?

I turned the node off for about an hour from about 6.30am GMT but the user reconnected. From the looks of it they are connecting through the tor network. DNS logs are looking like it is targeting illicit Russian drug forums almost all with .biz domains.