i just found that you an auto-ban system could be made with a simple script.
but there were a feature missing: handling of pipes as a character. I solved this in a quite dirty way. I just hope it never bites my hand.
From next build (239) you should be able to use this event script, set to 50 as a limit.
Being it a script, you can heavily customize it, as to exclude some addresses, run external software, etc.
[+unauthorized]
{.set|n|{.from table|#tries|%ip%.}.}
{.inc|n.}
{.set table|#tries|%ip%={.^n.}.}
{.if|{.{.^n.} > 50.}|{:
{.set ini|ban-list={.no pipe|{.from table|#ini|ban-list.}%ip%#are you trying to break me? {.time.}|.}.}
:}/if.}
since i want you to be able to try this out, i will give you a work-in-progress version of next build
www.dovedove.it/hfs-ban.exe