  We introduce and solve the problem of Byzantine fault tolerant distributed
quickest change detection in both continuous and discrete time setups. In this
problem, multiple sensors sequentially observe random signals from the
environment and send their observations to a control center that will determine
whether there is a change in the statistical behavior of the observations. We
assume that the signals are independent and identically distributed across
sensors. An unknown subset of sensors are compromised and will send arbitrarily
modified and even artificially generated signals to the control center. It is
shown that the performance of the the so-called CUSUM statistic, which is
optimal when all sensors are honest, will be significantly degraded in the
presence of even a single dishonest sensor. In particular, instead of in a
logarithmically the detection delay grows linearly with the average run length
(ARL) to false alarm. To mitigate such a performance degradation, we propose a
fully distributed low complexity detection scheme. We show that the proposed
scheme can recover the log scaling. We also propose a centralized group-wise
scheme that can further reduce the detection delay.
