ABSTRACT
Ultrasonic distance sensors use an ultrasonic pulse's time of flight to calculate the distance to the reflecting object. Widely used in industry, these sensors are an important component in autonomous vehicles, where they are used for such tasks as object avoidance and altitude measurement. The proper operation of such autonomous vehicles relies on sensor measurements; therefore, an adversary that has the ability to undermine the sensor's reliability can pose a major risk to the vehicle. Previous attempts to alter the measurements of this sensor using an external signal succeeded in performing a denial-of-service (DoS) attack, in which the sensor's reading showed a constant value, and a spoofing attack, in which the attacker could control the measurement to some extent. However, these attacks require precise knowledge of the sensor and its operation (e.g., timing of the ultrasonic pulse sent by the sensor). In this paper, we present an attack on ultrasonic distance sensors in which the measured distance can be altered (i.e., spoofing attack). The attack exploits a vulnerability discovered in the ultrasonic sensor's receiver that results in a fake pulse that is produced by a constant noise in the input. A major advantage of the proposed attack is that, unlike previous attacks, a constant signal is used, and therefore, no prior knowledge of the sensor's relative location or its timing behavior is required. We demonstrate the attack in both a lab setup (testbed) and a real setup involving a drone to demonstrate its feasibility. Our experiments show that the attack can interfere with the proper operation of the vehicle. In addition to the risk that the attack poses to autonomous vehicles, it can also be used as an effective defensive tool for restricting the movement of unauthorized autonomous vehicles within a protected area.
ABSTRACT
La enfermedad hepática grasa no alcohólica (NAFLD) es un desorden hepático crónico con características histológicas similares a las inducidas por el consumo excesivo de alcohol, pero que ocurre en individuos que no consumen alcohol en forma significativa y que puede comprender desde esteatosis, esteatohepatitis o cirrosis. Describir las características epidemiológicas, clínicas, de laboratorio, e histológicas de pacientes con diagnóstico histológico de NAFLD. Se realizó un estudio prospectivo, descriptivo y analítico que incluyó 146 pacientes con diagnóstico de NAFLD por biopsia hepática y con consumo de alcohol a 40 gramos/día. La prevalencia de la enfermedad en la población estudiada fue de 8 por ciento. La edad promedio de los pacientes fue 45 años, predominando el sexo masculino (62 por ciento); en el 92 por ciento las transaminasas estuvieron elevadas y la curva de tolerancia glucosada estuvo alterada en el 88 por ciento. Los principales factores de riesgo fueron Diabetes mellitus (19 por ciento), hiperlipidemia (66 por ciento), sobrepeso (62 por ciento), uso de medicamentos como tamoxifen, antiretrovirales y esteroides (8 por ciento). Los pacientes con cirrosis hepática fueron generalmente de mayor edad, asi como 50 por ciento fueron hombres, y presentaron más frecuentemente Diabetes mellitus e hiperinsulinismo. La NAFLD es una enfermedad relativamente frecuente, que está asociada generalmente a Diabetes mellitus, hiperlipidemia y sobrepeso y que requiere la realización de biopsia hepática ante su sospecha clínica, dada su relación con formas avanzadas de enfermedad hepática y sus potenciales complicaciones