Advanced Consideration of a Caller Pre-Validation Against Direct Spam Over Internet Telephony

Spam over Internet Telephony as the distribution of unwanted voice messages over Voice over Internet Protocol networks is an upcoming threat. It is harder to prevent than e-mail spam since its content is not available before the victim is annoyed. This is even more difficult if the spam is sent directly to the victim’s user equipment, bypassing the proxies of the service provider. Hence, this messages cannot be filtered, since the proxies are no longer participating in the transaction. This article presents a pre-validation mechanism, which ensures a minimum level of trust about the caller. It assumes that a legal registered user does not send any spam, since his service provider will penalize him if he does so. Therefore, the pre-validation mechanism sends some requests to the presence server of the provider and the user equipment of the caller to validate their existence. This enables the knowledge to allow a call attempt of an unknown user.