since when is access to ftp://ftp.astaro.com/pub/UTM/v9/ password protected?
Not sure about that. I've always used https://ftp.astaro.com/pub/UTM/v9/ and it works fine.
That is because you are using a browser instead of Windows Explorer. I cannot download via SSL either.
Sophos disabled the FTP Access to ftp.astaro.com.