Updated notice on Cisco and land.c

This is an update to the previous notice. I originally planned just to have
this updated on the Web site and to post a pointer to the updated Web page,
but the Web posting seems to be taking a really long time, and I don't want
to delay the notice any longer. This version will eventually (probably by the
time most of you read this) be posted at

   http://www.cisco.com/warp/public/770/land-pub.shtml

That URL will be updated with future versions. We probably won't send the
whole text out again.

Important differences between this notice and the last one:

   o There are definitely versions of classis Cisco IOS software that are
     badly affected by the land.c attack.

   o The notice contains detailed information about which IOS versions are
     affected.

   o Catalyst 5000s, and probably other Catalyst switches, are affected.

   o Various editing and advice changes... nothing really substantive.

        -- John B.

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Field Notice:
TCP loopback DoS Attack (land.c) and Cisco Devices

November 22, 1997, 08:00 AM US/Pacific, Revision 2