■As you know, there was a massive customer information leakage in a Japanese internet service provider Yahoo!BB. It is said the personal information of 4.5 million customer was leaked by internal personnel intentionally. The main cause of this massive information leakage is not poor information security but malicious internal personnels. Even in the companies which have a state of the art information security infrastrucuture, the internal personnels who have strong complaint about the company’s top management can easily leak important information in order to damage the company. As long as technical countermeasures are concerned, all that every company has to do is to implement the generally implemented security measures because these days the technologies related to information infrastructure are highly standardized (e.g. routers, firewalls and anti-virus softwares). The most important measures to ensure the information security is to continue motivating the employees by good management. Only one malicious employee can disable every IT security measures in the company by bringing out some paper document. For example, disproportionate investment in the information security can increase the risk of information leakage by internal personnels because such a disproportion itself indicates bad management.