A collective of security researchers issued a letter Friday from the DefCon hacker conference in Las Vegas urging the automotive industry to adopt five principles for building safer computer systems in vehicles.The group is operating under the name I Am the Cavalary and includes researchers and others concerned about the security of devices that have a direct impact on public safety. Over the last few years, a growing number of security researchers have investigated potential vulnerabilities in the electronic devices built into modern cars to control everything from entertainment systems to critical safety functions like brakes, steering and lights.[Researchers to name the most hackable cars at Black Hat]As automakers rush to build wireless functionality in some car systems to connect them with mobile phones and the larger Internet, there are increasing concerns that potential vulnerabilities combined with a lack of segmentation of internal car networks could open up attack vectors that expose vehicles to remote hacking, endangering driver safety.At the Black Hat security conference Wednesday, researchers Charlie Miller and Chris Valasek presented an analysis of wireless attack surfaces in 24 car models from different manufacturers. They ranked the 2014 models of the Infiniti Q50 and Jeep Cherokee and the 2015 model of the Cadillac Escalade as the most hackable cars.In its open letter to the auto industry, the I Am the Cavalry group urged car makers to build computer systems with security considerations in mind based on the principle of safety by design.Vehicle computer networks should use isolation and segmentation mechanisms to ensure that non-critical systems cannot impact the performance of critical systems, the group said.This segmentation should be physical rather than through logical controls, as past security research has shown that logical isolation can often be bypassed, said Joshua Corman, chief technology officer at Sonatype and co-founder of I Am The Cavalry.Car makers should also make sure that they can easily deploy security updates for computer systems if needed without requiring car recalls, the research group said in its letter. Finally, in case something does go wrong and a forensic investigation is required, car systems should have logging features that preserve evidence.Automakers should encourage third-party collaboration by publishing clear vulnerability disclosure policies for security researchers to follow. Tesla Motors is one company that has already done this, but others should follow suit, the group said.Members of I Am the Cavalry aim to provide their technical expertise to various industries and legislators as a public service, but they also invite participation from the public itself. The group's open letter to the automotive industry was also published as a petition on Change.org.The group is not only focused on the safety of car computer systems and is actually interested in three other groups of devices that can impact human life: medical devices including implantable, diagnostic, imaging and radiological ones; home devices like consumer electronics, alarm systems, door and garage locks, thermostats and heating and ventilation systems; and public infrastructure systems like those used in aircraft, public transportation, power and electricity, aviation, traffic monitoring, utility services and waste and sewage.[The 'autonomous,' hackable car]During a talk at DefCon Saturday, I Am the Cavelry co-founders Joshua Corman and Nicholas Percoco, the vice president for strategic services at Rapid7, will provide an overview of the group's first year of activity and the strategies it has built to advance its public safety goals."This initiative is not only about finding bugs," Corman said. It's about building relationships between researchers, industry and government, which is much harder, he said.