When a post gets old, instead of simply closing the discussion, send comments and trackbacks to the moderation queue. This will greatly reduce spam.
For documentation and tips, please refer to the official plugin page for Auto Moderate Comments
Installation is, as usual :
- Upload files to your
/wp-content/plugins/directory (preserve sub-directory structure if applicable)
- Activate the plugin through the ‘Plugins’ menu in WordPress
- Refer to the official plugin page for documentation, usage and tips