The paper simply analyzes the different of EMI,EMC,EML and Tempest and the mechanism of EML of computer. Some kinds of protection measure are presented. We should be aware of the big threat of active attacks.

• 简要分析了计算机 EMI,EMC,EML和 TEMPEST之间的区别及计算机主要信息泄漏源的泄漏机理 ,并介绍了相应的硬件防护技术及新型软件防护技术 ,分析了它们各自的优势与劣势 ,提出我们应注意到窃取者的主动攻击给计算机信息泄漏问题造成的更大威胁