Wireless sensor networks are built using tiny wireless sensor devices which have limited computational power and energy resources, as a result of which they can be subjected to various security compromises, including denial-of-service attacks. A particularly detrimental active denial-of-service attack that damages the sensing fidelity of wireless sensor networks is known as the Actuation attack, where hostile actuator (or actor) nodes belonging to a foreign network directly perturb or distort the environmental conditions being monitored. In this thesis we explore the loss of availability and reliability of wireless sensor networks ensuing from a proposed resilient Actuation attack which uses randomness and discontinuity to remain imperceptible. We demonstrate how the attack is designed to collect intelligence, without compromising any nodes or data packets, and to exercise caution to evade detection. We show how various factors, such as the frequency of actuation, topology of sensor network, forwarding scheme used by the network, and density of hostile nodes impact the efficacy of the attack. We discuss several possible techniques to defend against the proposed Actuation attack, and analyze their effectiveness. Finally, we conclude that it is increasingly difficult to control or detect an attack of this form owing to its random and asymmetric nature.