WordPress Spam Users

Just over a year ago I configured my blog to only allow signed in users to comment to reduce spam [1]. This has stopped all spam comments, it was even more successful than expected but spammers keep registering accounts. I’ve now got almost 5000 spam accounts, an average of more than 10 per day. I don’t know why they keep creating them without trying to enter comments. At first I thought that they were trying to assemble a lot of accounts for a deluge of comment spam but that hasn’t happened.

There are some WordPress plugins for bulk deletion of users but I couldn’t find one with support for “delete all users who haven’t submitted a comment”. So I do it a page at a time, but of course I don’t want to do it 100 at a time so I used the below SQL to change it to 400 at a time. I initially tried larger numbers like 2000 but got Chrome timeouts when trying to click the check-box to select all users. From experimenting it seems that the time taken to check that is worse than linear. Doing it for 2000 users is obviously much more than 5* the duration of doing it for 400. 800 users was one attempt which resulted in it being possible to select them all but then it gave an error about the URL being too long when it came to actually delete them. After a binary search I found that 450 was too many but 400 worked. So now it’s 12 operations to delete all the spam accounts. Each bulk delete operation is 5 GUI operations so it’s 60 operations to delete 15 months of spam users. This is annoying, but less than the other problems of spam.

UPDATE `wp_usermeta` SET `meta_value` = 400 WHERE `user_id` = 2 AND `meta_key` = 'users_per_page';

Deleting the spam users reduced the size of the backup (zstd -9 of a mysql dump) for my blog by 6.5%. Then changing from zstd -9 to -19 reduced it by another 13%. After realising this difference I configured all my mysql backups to be compressed with zstd -19, this will make a difference on the system with over 30G of zstd compressed mysql backups.

• [1] https://etbe.coker.com.au/2024/07/23/blog-comments-2/