General Lo Hsien-che, the most senior Taiwanese military figure to be charged with spying, was the one you would least expect to be a spy. He was the head of communications and electronic information for the secret Po Sheng project to build an electronic warfare system to co-ordinate Taiwans military forces and enable real time intelligence sharing with the US Pacific Command before his arrest.
The damage is enormous for the United States because it may have compromised US secret warfare codes. We know the General had access to it, and made at least one transaction with Chinese intelligence officials who paid an estimated $200,000 dollars for each disclosure he made to them.
The 'holy grail' would be the secret codes.
One Taiwanese General said if General Lo had indeed given warfare codes to China, the repercussions would be "massive". At this point we really can't assume the codes were not compromised. The risks to national security is too great.
It is certainly reason enough to change the codes as soon as possible.
The General faces execution or life in prison.