在近幾年來許多學者專注於車輛隨意網路(Vehicular Ad Hoc Networks)，它能可提供駕駛所關心的交通資訊。其中一種型態的車輛隨意網路為混合式車輛隨意網路(hybrid Vehicular Ad Hoc Networks)，此網路由車輛與固定的路旁設備(Road-Side Unit)所組成。車輛與路旁設備透過彼此的分享交通資訊，建立智慧型交通安全系統以增加道路安全或減少雍塞。由此可知，此交通資訊是必需受到安全系統的保護，否則被惡意車輛丟棄，導致駕駛忽略此資訊，可能會造成嚴重的交通意外，進而危害生命。雖然目前已存在許多異常行為偵測系統來面對此議題，然而，攻擊方式也會隨之變的更加複雜，惡意車輛想躲避異常行為偵測系統的偵測並能夠阻擋資訊的傳遞，導致做隨機丟棄訊息的攻擊。基於此理由，我們提出了一個新的異常行為偵測系統名為MEDIA來減輕此威脅造成的影響。本系統利用路旁設備與車輛的共同合作，找出與隔離惡意車輛。依模擬結果顯示，即使此環境存在高達百分之四十的惡意車輛，本系統還是能夠有效地提升網路效能與隔離惡意車輛。

In recent year, many academic researchers are focus in vehicular ad hoc networks (VANET). It can offer traffic information to drivers that care about. One kind of VANET is hybrid VANET. It consists of mobile vehicle and static road-side unit (RSU). They share traffic information with each other to build smart traffic safety system to increase road safety or less congestion. This traffic information must be protected by misbehavior detection system, otherwise it is discarded by malicious vehicles to lead drivers pass over this information and make serious traffic accidents to endanger life safety possibly. Although there are existed many misbehavior detection systems to face this issue, however, attack will also becomes complicated. Malicious vehicles want to escape the detection of misbehavior detection system and disrupt message propagation. It leads to do message random-dropping attack. For this reason, we propose a novel misbehavior detection system called MEDIA to mitigate influence of this threat. This system uses road-side unit (RSU) and vehicle to discover and isolate malicious vehicles collaboratively. The results of simulation show the MEDIA can enhance network performance and isolate malicious vehicles effectively even though up to 40% of malicious vehicle exists in the environment.

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