[1]¿p#1 Performance degradation attacks selectively and stealthily reduce service quality, seeking to avoid abrupt interruptions that facilitate detection. In Software-Defined Networking (SDN), the centralization of the control plane and the programmability of the data plane increase the attack surface, especially via controller management interfaces (e.g., REST APIs). This letter investigates an application-oriented attack based on intermittent injection of drop rules via the ONOS controller’s REST API. Unlike denial of service by saturation, this approach preserves global connectivity and keeps conventional metrics (such as ICMP RTT) apparently stable. Experiments with Mininet and ONOS show that the perceived availability of an HTTP service can be significantly degraded even without obvious signs of infrastructure failure. The results highlight the stealthiness of the attack and the limitations of connectivity-based monitoring alone.