  Introduction of PMUs to cyber-physical system pro-vides accurate data
acquisition, while posing additional risk of being the victim of cyber attack.
Both False Data Injection Attack (FDIA) and GPS-spoofing or timing attack can
provide malicious data to the cyber system, though these two attacks require
different post-attack contingency plan. Thus accurate detection of timing
attack and separating it from conventional FDIA has become a very important
research area. In this article, a successful detection of timing attack
mechanism is proposed. Firstly, a method to distinguish timing attack and FDIA
using unwrapped phase angle data is developed. Secondly, utilizing low rank
Henkel matrix property to differentiate timing attack from electrical events is
also presented. Finally, an experimental validation of proposed model is
performed on IEEE 13 bus system using simulated GPS-spoofing attack. It can be
observed that the timing attack can increase the rank 1 approximation error of
Henkel matrix of unwrapped angles by 700% for 3 sec delay in GPS time-stamp.
The rank 1 approximation error is increased by 500% for 2 sec delay and the
increase is insignificant for 1sec delay attack. FDIA doesn't show any
significant change in the low rank approximation profile of Henkel matrix.
