North American Network Operators Group
Date Prev | Date Next |
Date Index |
Thread Index |
Author Index |
Historical
Re: smurf
- From: Phil Howard
- Date: Mon Dec 08 13:38:49 1997
Adrian Chadd writes...
> A couple of problems:
>
> * Filtering ALL ICMP is pretty silly, ICMP is there for more than just
> pings, and some of it is important.
Such as MTU Discovery. If your customers try to go down a path where the
MTU is smaller than what they are sending, and if their packets prohibit
fragmentation, ICMP is the only way to inform their stack to reduce the
size of the MTU. Otherwise they may failures ranging from intermittent
to totality. Intermittent ones would often be seen when just a small
amount of data sometimes gets through. For example, an HTTP request could
be sent in a small packet, but posting a large form would not.
How many tech support people would know that the ability to get a page
and the inability to post a form could be caused by the customer's own
ISP blocking ICMP network unreachable?
So you need to leave "network unreachable" coming in.
Ref: "TCP/IP Illustrated, Volume 1, The Protocols", by W. Richard Stevens
See: page 340.
> * If people start doing this, someone with a smidgen of time on their
> hands will write a ping flooder that uses random TCP or UDP packets
> with spoofed from addresses.
Already been done. I've had one of those for 4 years.
The ultimate solution to network security was published a few months ago
in the Dilbert series.
--
Phil Howard | suck5it2@spammer8.edu end7it92@s0p0a2m0.com suck1it8@no6place.net
phil | end3it30@no3where.edu stop7it1@dumb6ads.net ads6suck@no8where.com
at | end6it68@noplace0.net die6spam@anywhere.org no1spam0@spam9mer.com
milepost | no1way40@spammer0.org end2ads9@spammer2.com blow8me2@no3place.com
dot | suck3it7@no62ads4.net no7spam7@noplace0.edu no7spam8@noplace1.net
com | blow2me9@spammer0.com stop1659@anyplace.com crash345@lame2ads.com
|
