We've got many complains from Bank of America about this: http://forum.joomla.org/viewtopic.php?f=621&t=791651
How to protect our server against such attacks ?
Maybe we should start mod_security ?
for porotect your server ,
you can install some script such as csf/lfd and Customize standard port for Barrier of attacker
for mod_securityyou can install mod_seurity under apache and compile it with many ways
kloxo-mr no graphical menu option for install it , such as cpanel but
kloxo-mr have'nt any problem with mod_security or other mod
apache and nginx support mod_security
note : for install and compile mod_security you must install many requirement such az Pcre , Lua , Libtool ,.... and use latest version in
http://www.modsecurity.org