Reference: SuppressDefaultFTPBanner Metabase Property (IIS 6.0)

By default, the FTP service sends a "220 Microsoft FTP Service" banner when clients connect to the server. The SuppressDefaultFTPBanner property allows you to disable the display of the default FTP banner.

When SuppressDefaultFTPBanner is set to true, the message sent to the client will only include the number "220", not the "Microsoft FTP Service" part of the banner name. ...