Our FTP has been comprimised??

[TegGEr]

Yesterday I checked our FTP log we are using IIS 5.0 with service pack 2....

and I found this on the log file

08:06:18 66.19.xx.xx [1 ]MKD 011125000526p 550

also on our FTP root there are COM1 folders that I cannot delete
it seem someone is tagging us

is there any way to delete these COM1 folders also I noticed that in the security options for our ftp folder there is a user that has this S-1-5-21-x--etc.... in it and I cannot delete it..

it says because this object is inhiriting permissions from its parent to remove.... so now that I have removed now I cannot access our ftp folder!!!

any suggestions

thanks...