Out of sight, but not out of mind: Traces of nearby devices' wireless transmissions in volatile memory

An IEEE 802.11 wireless device can leave traces of its presence in the volatile memories of nearby wireless devices. While the devices need to be in radio range of each other for this to happen, they do not need to be connected to the same network-or to any network at all. Traces appear in the form of full wire-type frames; a residue of the signals in the ether. We examine types of information that can be extracted from such residual frames and explore the conditions under which traces develop and persist. Their availability is determined by factors in both in the external environment (the types of signals in the ether) and the internal environment (the configuration and particulars of a device's wifi stack). To isolate some of these factors, we have created memory dumps of devices in various environments and configurations. Analysis of the dumps has offered insights into the conditions determining creation and decay of the traces. The results indicate that they will be available in a limited number of real-world scenarios. We conclude with practical advice on triaging and preservation.