  We consider a single-cell massive MIMO system in which a base station (BS)
with a large number of antennas transmits simultaneously to several
single-antenna users in the presence of an attacker.The BS acquires the channel
state information (CSI) based on uplink pilot transmissions. In this work, we
demonstrate the vulnerability of CSI estimation phase to malicious attacks. For
that purpose, we study two attack models. In the first model, the attacker aims
at minimizing the sum-rate of downlink transmissions by contaminating the
uplink pilots. In the second model, the attacker exploits its in-band
full-duplex capabilities to generate jamming signals in both the CSI estimation
and data transmission phases. We study these attacks under two downlink power
allocation strategies when the attacker knows and does not know the locations
of the BS and users. The formulated problems are solved using stochastic
optimization, Lagrangian minimization, and game-theoretic methods. A
closed-form solution for a special case of the problem is obtained.
Furthermore, we analyze the achievable individual secrecy rates under a pilot
contamination attack, and provide an upper bound on these rates. Our results
indicate that the proposed attacks degrade the throughput of a massive MIMO
system by more than half.
