Wireless sensor networks often have to be protected not only against an active attacker who tries to disrupt a network operation, but also against a passive attacker who tries to get sensitive information about the location of a certain node or about the movement of a tracked object. To address such issues, we can use an intrusion detection system and a privacy mechanism simultaneously. However, both of these often come with contradictory aims. A privacy mechanism typically tries to hide a relation between various events while an intrusion detection system tries to link the events up. This paper explores some of the problems that might occur when these techniques are brought together and we also provide some ideas how these problems could be solved.