We consider a network of Internet of Things devices transmitting to an IoT Gateway (IoT-GW). Such communications can potentially be overheard by one or multiple eavesdroppers. Our goal is to design an artificial noise (AN)-aided transmit strategy in order to enhance security against eavesdropping. We propose a communication design where the potential eavesdrop- pers are deactivated by means of jamming operations performed by 1) an In-Band Full Duplex (IBFD) IoT-GW and/or by 2) cooperative helpers featuring multiple antennas. We show that the solution where only the IBFD IoT-GW generates AN is feasible for small IoT networks and when a neutralization zone around each IoT-device is assumed. In the case with helpers instead, we show that the Average number of Secure Connections (ASC) increases at least exponentially with the density of the helpers.