Malware is software used to disrupt computer operations, gather sensitive information, or gain access to private systems. The Hijack RAT Android malware collects sensitive data like contacts and bank apps installed on a device, sends this to a server, then downloads a repackaged bank app version and prompts the user to install it. This malware uses techniques like hiding its icon, self-updating, and complex coding to avoid detection by antiviruses and uninstalling from the device.