  IP networks became the most dominant type of information networks nowadays.
It provides a number of services and makes it easy for users to be connected.
IP networks provide an efficient way with a large number of services compared
to other ways of voice communication. This leads to the migration to make voice
calls via IP networks. Despite the wide range of IP networks services,
availability, and its capabilities, there still a large number of security
threats that affect IP networks and for sure affecting other services based on
it and voice is one of them. This paper discusses reasons of migration from
making voice calls via IP networks and leaving legacy networks, requirements to
be available in IP networks to support voice transport, and concentrating on
SPIT attack and its detection methods. Experiments took place to compare the
different approaches used to detect spam over VoIP networks.
