1929
Senate Democrats are still rebuilding their computer system after hackers demanded a ransom earlier this month to unlock the network .
 ( ransom: demanded a ransom,  earlier this month: time, hackers: attacker, network: victim, computer system: victim, Senate Democrats: attacker) 
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: demanded a ransom,  earlier this month: time, hackers: attacker, network: victim, computer system: victim, Senate Democrats: attacker) 