This paper focuses on one of the most harmful categories of Denial of Service attacks, commonly known in the literature as “stealth” attacks. They are performed avoiding to send significant volumes of data, by injecting into the network a low-rate flow of packets in order to evade rate-controlling detection mechanisms. This work presents an intrusion tolerance solution, which aims at providing minimal level of services, even when the system has been partially compromised by such attacks. It describes all protection phases, from monitoring to diagnosis and recovery. Preliminary experimental results show that the proposed approach results in a better performance of Intrusion Prevention Systems, in terms of reducing service unavailability during stealth attacks.