Information & Communication Technology (ICT) plays a key role in modern power system. Component failure and malicious attack of cyber system could trigger outage, and sometimes, catastrophic blackout in powers system. Previous research shows that self-organized criticality of blackout arise from cascade overload and cascade outage. Whereas, recently observation show the other factors, including malicious sabotage, could contribute to SOC of blackout along without cascade outage. Stuxnet worm, as a new paradigm of malicious software that can spread in the physical isolated network, could initiate coordinated attack and result in ultra large blackout than expected. The cyber security issues of power system should be revisited correspondingly. (4 pages)