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Once installed on the infected computer , the virus encrypts the users ’ files and demands payment in bitcoin to allow the victims to access their data .
 ( ransom: demands payment,  victims: victim, in bitcoin: payment method, virus encrypts the users ’ files: attack pattern, computer: victim) 
Locate the role in the text that participated in the event based on the event type and return it in the event list. 
 Option: Event type: phishing, data breach, ransom, discover vulnerability, patch vulnerability, Arguments type: vulnerable system, capabilities, vulnerability, number of victim, issues addressed, compromised data, damage amount, common vulnerabilities and exposures, victim, patch number, number of data, tool, discoverer, time, purpose, place, payment method, releaser, vulnerable system version, attacker, supported platform, patch, price, vulnerable system owner, trusted entity, attack pattern. 
Text: {0} 
Answer:
 ( ransom: demands payment,  victims: victim, in bitcoin: payment method, virus encrypts the users ’ files: attack pattern, computer: victim) 