1. Minotaur Analysis - Malware Repository.
http://minotauranalysis.com
2. VX Vault - Online Repository of Malware Samples.
http://vxvault.siri-urz.net
3. Malware Tips - Your Security Advisor.
http://malwaretips.com/forums/virus-exchange.104/
4. MalwareBlackList - Online Repository of Malicious URLs.
http://www.malwareblacklist.com
5. Police ransomware threat assessment. Europol Public Information (2014)