  In this paper, we focus on the localization of a passive source from time
difference of arrival (TDOA) measurements. TDOA values are computed with
respect to pairs of fixed sensors that are required to be accurately
time-synchronized. This constitutes a weakness as all synchronization
techniques are vulnerable to delay injections. Attackers are able either to
spoof the signal or to inject asymmetric delays in the communication channel.
By nature, TDOA measurements are highly sensitive to time-synchronization
offsets between sensors. Our first contribution is to show that timing attacks
can severely affect the localization process. With a delay of a few
microseconds injected on one sensor, the resulting estimate might be several
kilometers away from the true location of the unknown source. We also show that
residual analysis does not enable the detection and identification of timing
attacks. Our second contribution is to propose a two-step TDOA-localization
technique that is robust against timing attacks. It uses a known source to
define a weight for each pair of sensors, reflecting the confidence in their
time synchronization. Our solution then uses the weighted least-squares
estimator with the newly created weights and the TDOA measurements received
from the unknown source. As a result, our method either identifies the network
as being too corrupt to localize, or gives a corrected estimate of the unknown
position along with a confidence metric. Numerical results illustrate the
performance of our technique.
