Answer:
Trojan horse
Step-by-step explanation:
When Emma downloaded a new game from an unfamiliar website. Trojan horse is automatically installed on Emma computer. Trojan horse is a very powerful malware that can harm the system it makes the system in the idle state .The Trojan horse makes the computer system in the slow state, even it has the capability to hack the overall system that's why the credit card of Emma has been stolen.