Hi Don,
There are several ways to kick these spaming Russians out of your Moodle.
1. Use PhpMyAdmin and sort the users according to their country codes, then zap all the users from Russia out of the database.
2. Use the Moodle site administration block, follow from users --> accounts --> bulk user action, then filter out all the users with .co.cc email damain, or users from Russia.
3. Use the Moodle site administration block, follow from users --> authentication --> no login, and set up this no login plugin. (strangely, this plugin is not working with my system (:<) Moodle 1.9)
4. Use the Moodle site administration block, follow from users --> authentication --> manage authentication. Scroll down the page and find the section "allowed email domains". You can specify here your school domain to be the only candidate for registration. Or, scorll down one more notch and find "dinied email domains". Here you can list black-listed domain names such as .co.cc. and block them from coming in.
Hope this helps you out of the trouble.
Cheers,
(すみません。私のシステムは英語なので英語の方が説明し易かったので英語で書きました。)