Dealing with a large number of compromised accounts

Hi,

I'd like to know how I can generate/force new passwords for all accounts on my board.
For now I've put my board into holiday mode as it as been threatened to post the user info for 9.335 users from compromised game servers that people use that they share account info with.
Board: http://www.kitopen.com/
For the past two weeks I've dealt with numerous compromised accounts, banning those accounts outright and deleted 3.750 accounts that had 0 posts and never visited the forum, set the required number of posts to at least 10 before you can PM and other counter measures.
Other hack attempts have been made to inject javascript into fields and php code into posts.

http://www.kitopen.com/t3770-here-s-the-deal-lovies
http://www.kitopen.com/t3764-timurovich (about 25 of these, one for each board section).

I won't deal with the demands in the thread, as it isn't a question of if it will happen, but when.

It is not possible to do a mass password reset.  You can manually do it yourself.