One of the main challenges in network management of large scale networks is the introduction of new applications. This introduction may be performed with the use of new intelligent technologies applied on existing infrastructure, e.g. Intelligent Networks or with the use of totally new infrastructure, e.g. Wireless Mobile Ad Hoc Networks. Such large scale networks present increased requirements as regards their maintenance, infrastructure facilities, security and reliability. In order to meet such requirements new security mechanisms should be applied. These security mechanisms should be adjusted to the specific characteristics of the underline network. The relevant impact to the network’s performance, should be taken into consideration. The performance could be evaluated with various techniques according to the nature of the underline network. Throughout this thesis it presents a secure IN architecture using application level and CORBAbased security mechanisms. Furthermore, through simulations it measures the efficiency burden imposed by the employment of the security mechanisms in the case of Interactive Multimedia Retrieval. More over, it identifies several attacks that render multipath routing protocols vulnerable to collaborating malicious nodes. It proposes an on demand multipath routing protocol, the Secure Multipath Routing protocol (SecMR), and it analyzes its security properties. Finally, through simulations, it evaluates the performance of the SecMR protocol in comparison with existing secure multipath routing protocols.