  In this paper, the secure performance of multiuser multiple-input
single-output wireless communications systems assisted by a multifunctional
active intelligent reflection surface (IRS) is investigated. The active IRS can
simultaneously reflect and amplify the incident signals and emit artificial
noise to combat potential wiretapping. We minimize the total system power
consumption by designing the phase, amplitude, and IRS mode selection of the
active IRS elements, as well as the precoder and artificial noise vector of the
base station (BS). The design is formulated as a non-convex optimization
problem guaranteeing communication security. To tackle the problem, this paper
proposes an iterative alternating algorithm to obtain an effective sub-optimal
solution. The simulation results show that the proposed scheme offers superior
secure performance over all the considered baseline schemes, especially when
the number of eavesdropper antennas is more than that of the BS.
