This paper deals with the design and implementation of security mechanisms in networked embedded systems (e.g. Wireless Sensor Networks (WSN)), without the support of external “resource unconstrained” facilities. While most literature contributions propose to put intelligence (that is usually more consuming both in computational resources and in memory as well) outside the WSN, we have already reported in some previous works that, under certain limitations, a WSN can operate as a functionally “autonomous entity” not only for sensing operations. This paper provides a global overview of the related research project and then reports on recent design upgrades to what we denote as the “Secure Platform”, i.e. the SW platform over WSN that is able to support a wide range of applications in non-standard environment such as monitoring of critical infrastructures, data acquisition in hazardous environments under standard security conditions. The work presented here is a partial achievement of the internal project WINSOME (WIreless sensor Network-based Secure system fOr structural integrity Monitoring and AlErting) at our Centre DEWS, whose target is to develop a cross-layer secure framework for advanced monitoring and alerting applications.