Firewalls And FTP

[javedmma]

I understand that FTP leaves a Security hole because of its nature of starting two coneections, control and data.What would be the best method of doing FTP to a server on the internet from the inside network behind the firewall.Is proxy the best solution or passive FTP.If proxy is the best solution can somebody suggest me the best proxy software/Hardware available in the market.

Regards,

Javed

[beth-martin]

Stateful packet filters like the PIX and IOS firewall dynamically open connections to the Internet and don’t allow inbound traffic that is has not originated from the inside. They are aware of both regular and passive FTP and allow the control session and data session to occur without a problem. Proxy servers are very slow so I can’t see recommending that. Just be sure if you’re using the PIX to be on 5.1(2) or greater (see http://www.cisco.com/warp/public/707/pixftp-pub.shtml

[kasey.hohenbrink]

the simplest way is to download freeware ftp clients that support "passive mode" ftp.

Passive mode makes the ftp server send back data on the port that was nogotiated.

This makes it easy to configure your inbound ACL rules to allow tcp established.

You don't need a proxy server. Passive mode ftp works fine through firewalls and natted

gateways. As for the clients...Solaris and NT doen't come with passive mode ftp clients.

Try wsftp, cuteftp, ncftp.

Passive uses port 21 only, active uses 20 and 21.

[brian.walsh]

Passive mode is the best solution, because it does not open the inbound connection on port 20. In some cases it is not possible to use passive mode due to limitations in the server or client software, and if you are restricted to specific software this can be a problem. If you enable the FTP fixup command in the pix firewall, the pix will interpret the outbound port 21 control connection and subsequently allow requested port 20 data connections back through the firewall.