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Re: security.debian.org and active FTP?



martin f krafft <madduck@debian.org> [2002-09-06 20:30:36 +0200]:
> anyone have an answer why security.debian.org sends active FTP
> transfers from a high port rather than port 20?

IIRC there is nothing particularly interesting in that.  The ftpd will
open a connection back to your port and will use a randomly assigned
port on its end.  Remember that root access is needed to open a port
below 1024.  But having every program run as root opens up many
possibilities for security attacks against it.  Therefore there has
been a big movement to run as much of daemon code as possible
non-root.  Which means that more and more you will see use of
privileged ports diminish in order to accomplish that.  I am guessing
any change in behavior is due to this.

If you open up a "passive" ftp connection you should see all
connections from your end to the server and then all of them should go
to the published incoming port numbers in /etc/services.  But they
will be high port numbers on your end instead since you are the
originator.  Most browsers use passive ftp by default.  To open a
passive connection in ftp use "passive" as a command.  The wget
program has a --passive-ftp option.

Bob

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