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Though it is quite difficult to calculate the overall damage caused by ransomware in 2016 , some researchers state that cybercriminals received over $ 1 billion in ransom payments last year .
 ( ransom: ransom payments,  last year: time, cybercriminals: attacker, over $ 1 billion: price) 
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: ransom payments,  last year: time, cybercriminals: attacker, over $ 1 billion: price) 