This plugin is outdated and might not be supported anymore
TWPW Stop Remote Comments

TWPW Stop Remote Comments

Details
View on WordPress

Adds a “nonce” field to the comments form. If the “nonce” is missing on submit, the comment will return an error.
This will stop submissions from remote sites and cut down of the comments received from comment bots

Details

Plugin code:
twpw-stop-remote-comments
Plugin version:
1.0
Outdated:
Yes
WP version:
3.3 or higher
PHP version:
or higher
Test up to WP version:
3.3.2
Total installations:
10
Last updated:
2012-06-11
Rating:
Times rated:
0
comments
remote-comment-spam
spam