Public WiFi (IEEE 802.11) networks are an abundant data source that may serve different applications such as epidemic tracking and prevention, disaster response, crowdsensing, or ubiquitous urban services. Nevertheless, collecting and exploiting such data brings many privacy liabilities, considering that each transmitted frame has the MAC address (a unique device identifier) of the corresponding personal device, also considered sensitive information. Literature has shown that the MAC randomization performed by phone manufacturers is insufficient to protect devices’ identification. Data obfuscation is a promising solution to avoid storing advertised identifiers of devices and prevent attackers from acquiring sensitive data. Obfuscating such identifiers while also being able to differentiate frames sent by different devices poses a significant challenge for frame capturing by low-resource IoT devices in real-time. Since no popular off-the-shelf sniffer (wireshark or tcpdump) allows for on-the-fly obfuscation, we build a new custom-made sniffer module MITIK-SENS capable of on-the-fly obfuscating (hash and truncate) the required data needed of each WiFi frame to protect user privacy.