Site under attack by spammers

My site was an acquired site. The previous owners had installed a blog hosting software for forum members to use. It failed and was never fully decommissioned. Apparently, spammers discovered it and have created over 100,000 trackbacks and a number of accounts.

Since it is no longer used or promoted (or really useful to the site) What do you think I should do?

Redirect the traffic to the home page?
Redirect the traffic to an error page?
Redirect the traffic to a site map?

delete it.

spam trackbacks do you 0 benefit