無線行動隨意網路（MANET）是近年來興起的重要議題，它是由行動節點(如PDA、筆記型電腦)所建構而成。此網路能隨意的讓具有無線設備的裝置加入，再加上不需任何的固定裝置與集中型的無線網 路管理，因此常被應用在軍事方面、個人家庭網路或是緊急救援之上。
在本論文中，首先簡介了無線行動隨意網路的分類及特色。包括又可分為主動式的表格驅動式路由及被動式的需求式路由。然而它的網路模式可隨使用者的移動而改變，這些利於任意移動的特性卻也導致頻寬、電力及資源消耗的問題。
同時，這些特別的網路拓蹼特性也會引來惡意使用者的攻擊。在本論文中則是針對共謀性黑洞攻擊提出了保護方式，並且經由模擬結果得知此防護方法可有效的抵禦攻擊與增進整體網路環境的安全性。

The Mobile Ad Hoc Network (MANET) is a collection of mobile nodes. It is a simple peer-to-peer network. Ad hoc network has many uses, such as personal networks, household networks, military applications, and emergency rescue operations.
Since the network without any physical infrastructure and central base station, network management is done cooperatively by the other nodes. The feature about Ad hoc network is constraint resources, low bandwidth, and limited battery power. These kinds of networks are wide open to different types of attacks because unknown nodes can easily join the ad hoc networks. That is the reason why network security becomes a major concern.
In this article, we are going to present a mechanism which can detect a kind of Cooperative Black Hole Attack. About this attack, the multiple malicious node acting in a group, they can advertises itself have shortest and fresher route. When these malicious nodes received data packet from source node, they may drop them or intercept them. This attack may cause to reduce the packet delivery ratio and the throughput.
Our solution is basic on normal AODV, and it has a simply change on AODV protocol. Computer simulation used QualNet to show that our protocol provide better performance in the delivery rate than the normal AODV protocol which under the cooperative black hole attack.

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