Wireless Body Area Networks get more widespread and deal with sensitive patient data. Despite that, they are connected to the Internet and processing is partly outsourced into the cloud, raising security concerns. An aspect that seems to have been neglected is the possibility of steganographic transmissions via network covert channels in such networks, and which countermeasures could mitigate or even eradicate such channels. Such investigation seems necessary as network steganographic channels are often used by malware to harm functionality of devices or exfiltrate data to attackers. The present research seeks to fill this gap by performing a hiding pattern analysis which reveals that network covert channels are possible in wireless body area networks based on IEEE 802.15.6. We support the analysis by a simulation that demonstrates feasibility of one of the identified network covert channels. Furthermore, we discuss countermeasures against network covert channels in body area networks such as compartmentalization through virtualization.