Re: ZoneAlarm blocks FTP apps

From: Wolfgang Kueter (wolfgang_at_shconnect.de)
Date: 01/21/05 

Date: Fri, 21 Jan 2005 17:26:14 +0100

in2minds wrote:

>> For the record, in the "Firewall" section of ZoneAlarm: if I select
>> "Medium"
>> for the Internet Zone Security, then FTP works. It's only when I
>> leave it on
>> the (default) setting of "High" that it blocks FTP from listing site
>> contents.
>>
>
> it's not ZA,

Wrong.

> it's more than likely the remote server blocking your
> access because it can't do reverse DNS (or so I've been told).

Complete Nonsense.

> ZA set on High hides your IP address, so you'll just have to set it to
> medium when you're FTPing...

Again: Complete nonsense. If you IP is hidden, you don't get back a single
packet from any computer using whatever protocol. It is a problem that has
to do with the fact, that ftp use two (!) connections (command and the data
channel) using different ports and that there are two possibilities (active
and passive mode) about how the connection properties for the data channel
are handled and set up between client and server. When using active mode,
the client becomes the server and you need to allow an incoming connection
to Port 20.

> ... I have the same problem

which is that have no clue. Play around with ftp connecttions using both
modes and sniff the traffic. Read the RfC describing the ftp protocol,
analyse the results from your sniffer.

Wolfgang

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