True Android viruses (or more accurately, Trojans and Worms) use several common vectors to compromise a device: Malware Type Primary Method of Attack Disguise themselves as legitimate apps (games, utilities). Ransomware
If you are genuinely interested in cybersecurity and Android internals, you should never touch a "Virus Maker." Instead, you should study using legal sandboxes. virus maker android
Stay curious, but stay legal.