Applications over Wireless Sensor Networks (WSNs) are various and different. Many routing protocols have been proposed for WSNs since a many years. Medium Access Control (MAC) protocols can differ from a network to another. The transmission range can also be variable from a sensor to another depending on their battery capacities. All these various protocols have an influence on the WSNs. It is worthy to choose the appropriate protocol for each specific situation in order to ensure high security of the network. In this paper, we show that the type of applications has a real impact on WSN. In- deed, each kind of application with a specific routing protocol, MAC layer and transmission range value impact on security of network in terms of packets lost rate. We have undertaken a set of experimentations in order to show the importance of an appropriate configuration to deploy a WSN with a high security confidence degree. For the application layer, we have handled three types of applications. For the routing layer, we have handled only with AOMDV protocol. For MAC layer we use 802.15.4 protocols. We have conducted many simulations through the NS-2 simulator in order to analyze one relevant security indicators on WSNs: lost packet rate.