[Mailman-Users] ISO speciific RegExp to filter/discard bot subscribe requests

[Nelson Kelly]

Hello, We have a list running on Mailman version 2.1.20.

Over the last several days began receiving hundreds of bot subscription 
requests (all gmail addresses).

All of format like:
blech+12345678 at gmail.com
zark+98765432 at gmail.com

In attempt to solve this issue, entered the following regex lines in 
Privacy Options -> Subscription Rules -> ban_list

^.*blech
^.*zark

Temporarily did the job, but the bot(s) adapted and changed the prefix 
of the address string to:

crap+12345678 at gmail.com
grum+98765432 at gmail.com

Common to ALL of the bot subscribe requests is including within the the 
email address a "+" symbol.

So I tried entering RegExp ^.*+ but Mailman rejected this entry.

But was able to enter RegExp of ^.*/+
However that allowed all the bot spam requests through.

Unable to keep up with the bots changing the address prefix.

Can anyone recommend an example of a RegExp entry which would 
prevent/solve this dilemma?

Note: I've searched the Mailman-Users list archives and noted Mr. 
Yardley's recent posts, but not able to implement his solution as I 
don't have access the server. (so also unable to configure 
SUBSCRIBE_FORM_SECRET solution).

Thank you for any ideas.