Network covert channels are hidden communication channels in computer networks. They influence several factors of the cybersecurity economy. For instance, by improving the stealthiness of botnet communications, they aid and preserve the value of darknet botnet sales. Covert channels can also be used to secretly exfiltrate confidential data out of organizations, potentially resulting in loss of market/research advantage. Considering the above, efforts are needed to develop effective countermeasures against such threats. Thus in this paper, based on the introduced novel warden taxonomy, we present and evaluate a new concept of a dynamic warden. Its main novelty lies in the modification of the warden's behavior over time, making it difficult for the adaptive covert communication parties to infer its strategy and perform a successful hidden data exchange. Obtained experimental results indicate the effectiveness of the proposed approach.