I have an old site that is in danger of being compromised as many of the directories and files have permissions set to 777. However, when I try to change them to 555 via FileZilla I get the error
500 'SITE CHMOD 555 filename': command not understood
Googling it only has issue relavant to connecting to the server, but I can do that, as well as up and downloading files, fine. Im not sure what this means exactly. Is it that my account doesnt have sufficient permissions to make these changes?

chmodis a unix command. – w3d Feb 20 at 10:10