On Fri, 16 Nov 2001, Gerald Timothy Quimpo wrote:

> At 01:32 AM 11/17/01, Pong wrote:
>
> >if they allow you to connect to port 21 (the ftp control port),
> >there's no reason to block you from downloading from the data port.
> >simply put, something is blocking your access to the ftp data port that's
> >why it times out. try forcing a passive mode ftp data connection
> >by typing 'passive' repeatedly until the ftp session toggles it to
> >'Passive mode on'
> >
> >ftp> passive
> >Passive mode off.
> >ftp> passive
> >Passive mode on.
> >
> >once it's in passive mode, then do an 'ls'. if it succeeds
> >then, you now can download.  in passive mode, both connections
> >(control and data) to the ftp server is initiated from your
> >ftp client and helps you bypass any probable firewall in between
> >preventing the ftp server from initiating the data connection
> >to you instead.
>
> ahh, that's the problem.  i forgot that i was on a box that
> had input deny as the default policy (but with allow established
> connections. this was on FreeBSD).  i just tried that and i
> see that it's 5.2 on there so i guess i won't be grabbing
> that tonight.  i already have that.
>
> i've got some other questions about firewalls and networking
> and i may as well ask them now that the topic comes up.
>
> 1.  i've got ip-masq on my dialup-server.  when i do
>
>      netstat -a
>
>      i see connections from the server to internal boxes and
>      connections from the server to external boxes, but i don't
>      see masqueraded connections.  is there a way to see what
>      masqueraded connections are active?

ipchains -L -M -n

> 2.  in general, "input deny by default is more secure" than
>      input accept by default.  of course.  but if i've got
>      my firewall selectively allowing only trusted hosts to
>      connect to ports where daemons are listening
>
>         e.g., the only service on box B1 is HTTP and i've got
>         a firewall rule that says only IPs in the range
>         ABC.DEF.GHI.0-16 can connect to B1:80
>
>      what benefit is there in denying by default to ports where
>      no servers are listening?  (naturally, i'd let established
>      connections, started from inside, through the firewall).

none really

>
>      or maybe that's the wrong question.  better would be, how
>      would an attacker, ah, attack a box like that where there
>      are no open ports to connect to?  i don't think "deny by

Syn Floods, Ping floods, unless you deny icmp as well.  If your kernel is
old, ye old ping of death will do you..


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