[cobalt-users] How to defend against dictionary attacks?

[Glenn Parsons <gparsons@xxxxxxxxxxxxx>]

Hello All,

I am seeing, what I think are called 'dictionary attacks,' on my mail 
server for users on a regular basis. How can I prevent them, or guard 
against them? My logs are not providing an address to block. I can't tell 
whom is instigating this!

> Apr 14 00:59:14 mail sendmail[8099]: i3E4xEp08099: <hhb273rdmsxb@xxxxxxxxxx>.
> .. No such user here
> Apr 14 00:59:14 mail sendmail[8097]: i3E4xEp08097: <bernard@xxxxxxxxxx>... No
>  such user here
> Apr 14 00:59:14 mail sendmail[8097]: i3E4xEp08097: <louise@xxxxxxxxxx>... No
> such user here


Please advise.

Thanks,
Glenn Parsons