You need an ETA for Cocos (Keeling) Islands if you have a South Korean passport

To visit Cocos (Keeling) Islands for Business or Tourism, you require a visa. The Electronic Travel Authorization (eTA) is required for visa-exempt visitors entering Cocos (Keeling) Islands. It is an online application. If approved, you'll receive your eTA confirmation electronically. When you arrive in Cocos (Keeling) Islands, border crossing will ask for your passport and check their electronic records to ensure you have the proper visas. Note: Your eTA is electronically linked to your passport and when you receive a new passport, you must apply for a new eTA. For all other visas, visit the government site.