Applications overW ireless Sensor Networks (WSNs) are various and different. Manyr outing protocols have been proposed for WSNs since am anyy ears. Medium Access Control (MAC) protocols can differ from anetwork to another.T he transmission range can also be variable from as ensor to another depending on their battery capacities. All these various protocols have an influence on the WSNs. It is worthytochoose the appropriate protocol for each specific situation in order to ensure high security of the network. In this paper,weshowthat the type of applications has areal impact on WSN. Indeed , each kind of application with aspecific routing protocol, MAClayer and transmission range value impact on security of network in terms of packets lost rate. We have undertaken aset of experimentations in order to showthe importance of an appropriate configuration to deployaWSN with ahigh security confidence degree. Forthe application layer,wehavehandled three types of applications. Forthe routing layer,wehavehandled only with AOMDVprotocol. ForMAC layer we use 802.15.4 protocols. We have conducted manysimulations through the NS-2 simulator in order to analyze one relevant security indicators on WSNs: lost packet rate. 1I ntroduction AWSN is mainly composed of twotypes of components: resource constrained independent nodes (sensors) and high resourced sink nodes (base stations). Anode in anetwork communicates with each other through awireless medium, where the communication energy is greater than the computational energy.I na ddition to that, the energy required to transmit am essage is twice higher than the energy required for receiving am essage. In the same time, the route of anymessage sent to base stations is achallenging issue about anetwork lifetime for manyreasons. If we use the shortest routes where some nodes have small capacity batteries, we may reduce the network lifetime. If we use longer routes with manynodes, we will surely increase the network delays. Forthese reasons, routing objec-tivesare, in general, conducted by higher applications: streaming video applications need longer network lifetime butfire monitoring applications need faster response time. Va ri-ous routing mechanisms have been proposed for different applications. Theyare different according to their routing objectivesand routing techniques. As said below, the network features will guide to choose adequate routing techniques. The IEEE 802.15.4 standard offers the most common communication protocols for the MACa nd the physical (PHY) 130