On Tue, 13 Jan 2015 20:12:11 +0000
Joe <joe@jretrading.com> wrote:
> On Tue, 13 Jan 2015 14:27:42 -0500
> David Parker <dparker@utica.edu> wrote:
>
> > Thanks for the replies.
> >
> > The system is not using tcpwrappers, and it's also not a DNS issue.
> > The client PC does have a reverse DNS entry. A tcpdump packet
> > capture on the server shows the initial connection from the client
> > followed by a bunch of DNS traffic, all within the same second.
> > Then nothing happens for exactly 5 seconds, then the server sends
> > data back to the client.
> >
> > Just to be extra sure, I added an entry for it in /etc/hosts so DNS
> > wouldn't even be needed. Still made no difference.
> >
>
> Is it asking for an ident from the connecting server (TCP port 7)?
> This is an old-fashioned custom, when computers with MTAs also ran
> ident servers, which provided some fairly harmless information.
>
> Exim4 can certainly ask for an ident, and does nothing for a
> configurable timeout unless one is received, or the sender address is
> whitelisted. It is a simple anti-spam measure, as practically nothing
> runs ident servers today, and most malware will give up before a
> thirty-second timeout expires, whereas a legitimate MTA will wait
> for that long.
>
OK, where did the 7 come from? Should be port 113. I saw it just as the
mouse button clicked...
--
Joe
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