  Most attacks are launched inside the companies by the employees of the same
company. These kinds of attacks are generally against layer-2, not against
layer-3 or IP. These attacks abuse the switch operation at layer-2. One of the
attacks of this kind is Address Resolution Protocol (ARP) Spoofing (sometimes
it is called ARP poisoning). This attack is classified as the 'man in the
middle' (MITM) attack. The usual security systems such as (personal) firewalls
or virus protection software can not recognize this type of attack. Taping into
the communication between two hosts one can access the confidential data.
Malicious software to run internal attacks on a network is freely available on
the Internet, such as Ettercap. In this paper a solution is proposed and
implemented to prevent ARP Spoofing. In this proposal access control lists
(ACL) for layer-2 Media Access Control (MAC) address and protocol filtering and
an application called ARPserver which will reply all ARP requests are used.
