A new way to eavesdrop on people’s mobile phone calls has come to light in the form of Spearphone – an attack that makes use of Android devices’ on-board accelerometers to infer speech from the devices’ speakers. An acronym for “Speech privacy exploit via accelerometer-sensed reverberations from smartphone loudspeakers,” Spearphone was pioneered by an academic team from the University of Alabama at Birmingham and Rutgers University. The team tested three Android models: The LG G3; Samsung Galaxy Note 4; and the Samsung Galaxy S6. In all three cases, because the accelerometer and the speakers are located so close together, the sensor can “Feel” the audio. Spearphone attempts to compromise speech privacy by performing gender, speaker and speech classification, via signal processing along with machine learning, the team said. From an attacker’s perspective, gender classification helps the attacker to narrow down the set of speakers for unidentified speech samples, thereby increasing the recognition accuracy for speaker identification. Speaker classification meanwhile helps the attacker with more context about the communicated speech. Then there’s speech classification, which reveals the contents of the speech itself that may be considered private between the two communicating parties. In order to perform speech classification, we build a classification model based on a finite word list,” the researchers explained. Speech features from the obtained sensor readings for isolated words are compared against the labeled features of the word list by the classification model that provides the attacker with a possible rendition of the actual spoken word. We also study the feasibility of performing speech reconstruction by isolating possible words from natural speech and then using word recognition on isolated words to reconstruct speech.\”One way to implement this approach would be to mask or dampen the vibrations leaked from the phone’s speakers by surrounding the inbuilt speakers with vibration-dampening material. This form of speech masking would prevent speech reverberations emanated from the phone’s speakers, possibly without affecting the quality of sound.