Enlarge (credit: CyberHades) SAN FRANCISCO—Malware developers are always trying to outdo each other with creations that are stealthier and more advanced than their competitors’. At the RSA Security conference this week, a former hacker for the National Security Agency demonstrated an approach that’s often more effective: stealing and then repurposing a rival’s code. Patrick Wardle, who is now a security researcher at the macOS and iOS enterprise management firm Jamf, showed how reusing old Mac malware can be a smarter and less resource-intensive approach for deploying ransomware, remote access spy tools, and other types of malicious code.