Why is FTP working when it is not allowed in GUFW?

linustalman · 01-14-2014, 01:46 PM

Hi.

I have a a firewall on my wireless router (standard setting). I also have GUFW enabled (no additional settings made).

Recently I used this Android app named 'Ftp Server' to copy files to my smartphone from my PC via the router.

I am curious as to why FTP is working when it is not allowed as a rule in GUFW. I presume my router firewall allows it by default.

Can someone shed some light on this?

Thanks.

michaelk · 01-14-2014, 02:13 PM

I assume that the smartphone is connected via wifi so it is on your internal LAN. Your router's firewall has no affect in this case. If your transferring files to the smartphone then the incoming connection is already established and so the GUFW allows it.

linustalman · 01-15-2014, 09:31 AM

Quote:

Originally Posted by michaelk

I assume that the smartphone is connected via wifi so it is on your internal LAN. Your router's firewall has no affect in this case. If your transferring files to the smartphone then the incoming connection is already established and so the GUFW allows it.

Hi michaelk.

Yes, it's connected via wireless. Could you elaborate on 'incoming connection is already established'. Attached is a screengrab of my Gufw setup (for 'Incoming' it says 'Deny'). Also I am able to copy a file from my smartphone to my PC via Filezilla - should that be allowed?

michaelk · 01-15-2014, 01:39 PM

The screen shot is missing.

Basically, an established connection will allow incoming traffic from outgoing connections. For example someone might probe your computer for a ftp server. The firewall will block that but if you initiate a connection to a FTP server from the computer itself the firewall will allow that traffic back.

Is your incoming policy deny? Without seeing your rules I can not say why you can connect to the ftp server on the PC.

linustalman · 01-15-2014, 02:38 PM

Quote:

Originally Posted by michaelk

The screen shot is missing.

Basically, an established connection will allow incoming traffic from outgoing connections. For example someone might probe your computer for a ftp server. The firewall will block that but if you initiate a connection to a FTP server from the computer itself the firewall will allow that traffic back.

Is your incoming policy deny? Without seeing your rules I can not say why you can connect to the ftp server on the PC.

Sorry, here it is.

michaelk · 01-15-2014, 04:44 PM

It appears that the firewall should drop incoming connections.

linustalman · 01-17-2014, 03:27 AM

Quote:

Originally Posted by michaelk

It appears that the firewall should drop incoming connections.

So I should not be able to copy files from my smartphone to the PC? Do you think this a Gufw or ufw bug?

Code:

sudo ufw status verbose

Code:

Status: active
Logging: on (low)
Default: deny (incoming), allow (outgoing)
New profiles: skip