  We consider a class of malicious attacks against remote state estimation. A
sensor with limited resources adopts an acknowledgement (ACK)-based online
power schedule to improve the remote state estimation performance. A malicious
attacker can modify the ACKs from the remote estimator and convey fake
information to the sensor. When the capability of the attacker is limited, we
propose an attack strategy for the attacker and analyze the corresponding
effect on the estimation performance. The possible responses of the sensor are
studied and a condition for the sensor to discard ACKs and switch from online
schedule to offline schedule is provided.
