《孙子兵法·军形篇》说:“善守者,藏于九地之下;善攻者,动于九天之上,故能自保而全胜也。”其中“九地”是指至深之地,孙子用其来说明防御时要善于隐蔽企图,就像隐藏于深不可测的“九地”之下,使敌无法了解防守方的意图。现实的网络攻防战中,对抗双方都试图最大限度地隐蔽自身各种信息:一方要隐藏进攻的工具和战术,另一方则要隐秘防御方案和措施。所以,《孙子兵法·虚实篇》又说:“故善攻者,敌不知其所 ”The Art of War, military-shaped articles,“ said: ”Good defender, hidden under nine; good attacker, move in nine days above, it can protect themselves and victory also.“ ”“ Nine ” Refers to the deepest land, the grandson uses it to illustrate the defensive good at covert attempts, like hidden in the unfathomable “nine places,” so that the enemy can not understand the defensive intentions. In actual cyber warfare and defense, both sides of the rivalry try to hide all kinds of information to the utmost extent: one should hide offensive tools and tactics, and the other must secretly defend against the scheme and measures. Therefore, “Art of War actual articles” added: "so good attacker, enemy do not know what they are