How to protect registered IP addresses

Hui-Hui Hu hhui at
Thu Mar 13 14:49:32 UTC 1997

Princeton has a piece of code that ARP bombs unregistered hosts. IPs that
are broken get sent an ARP packet with the same IP and an ethernet 
address of 00:00:00:de:ad or something. This is usually enough to disable 
Windows 95 boxes (since they do a RARP call when they boot up to check 
for duplicates) and some other OSes too. This provides a quick filter 
before actually blocking things at the router level, which is more expensive.

Of course the clueful can easily get around this, but hey.

-Tung-Hui Hu / Arc Four / hhui at

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