550
" A part of carefully planned large - scale ransomware attack requires a separate bitcoin address for each victim , guaranteeing the miscreant controlling the operation would later be able to identify the payment and decrypt the correct system , " wrote security expert John Wetzel in a blog post .
 ( ransom: ransomware attack,  a separate bitcoin address: payment method, victim: 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: ransomware attack,  a separate bitcoin address: payment method, victim: victim) 