Slow and Fast IP addresses on http ?

It might also be port 113 -- some sites try to query your tcp port 113,
and wait for a timeout if the port is firewalled. A better solution
than blocking it is to send an immediate RST.

    --Steve Bellovin, http://www.research.att.com/~smb (me)
    http://www.wilyhacker.com (2nd edition of "Firewalls" book)

smb@research.att.com ("Steven M. Bellovin") writes:

It might also be port 113 -- some sites try to query your tcp port 113,
and wait for a timeout if the port is firewalled. A better solution
than blocking it is to send an immediate RST.

people who depend on tcp/113 deserve everything stupid that happens to them.
dropping SYN packets or returning a fixed string are both better than sending
an immediate RST. (false confidence being valued less than low confidence.)
i was rather shocked to discover tcp/113 clientness enabled by default in
postfix and sendmail. but even widespread ignorance does not call for
widespread coddling such as returning immediate RST's.

In the immortal words of Paul Vixie (vixie@vix.com):

> It might also be port 113 -- some sites try to query your tcp port 113,
> and wait for a timeout if the port is firewalled. A better solution
> than blocking it is to send an immediate RST.

people who depend on tcp/113 deserve everything stupid that happens to them.
dropping SYN packets or returning a fixed string are both better than sending
an immediate RST. (false confidence being valued less than low confidence.)
i was rather shocked to discover tcp/113 clientness enabled by default in
postfix and sendmail. but even widespread ignorance does not call for
widespread coddling such as returning immediate RST's.

What Paul said. Ident delenda est.

ftp://blank.org/pub/misc/identd.pl <-- suitable for use under inetd
and tcpserver, if all else fails.

-n

------------------------------------------------------------<memory@blank.org>
"Must I pray in Hebrew?" No, and wipe that look of terror off your face.
Fluency in Hebrew, of course, is vital to the proper understanding of Israeli
truck driver insults. (--David Bader, "How to Be an Extremely Reform Jew")
<http://blank.org/memory/&gt;\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-

If you are the only user of your machine, feel free to return whatever you
want. However, there are still people out there running these things
called servers, where multiple users have accounts, and ident is a
perfectly valid and useful protocol for providing some accountability
against non-root abuse.

You could also run a DNS server which doesn't return any kind of answer
for your reverse DNS if you so desired, but you should be prepared to have
the rest of the world delay your connections on certain services while
they try to figure out why you can't play nice like everyone else. Any
time you decide not to return an RST, you are making the decision to
violate rfc's and may be punished with timeouts accordingly. Rate limiting
RSTs is a perfectly valid method of handling this.