Malware researchers need to test their skills and develop defense with real specimen. They can collect malwares sample from honeypot or download those from URL sources. The following sites can be resourceful:

1. Contagio Malware Dump (Mobile Malware)
2. Kernelmode.info
3. Malshare
4. Malware.lu AVcaesar
5. MalwareBlacklist
6. Malwr
7. Open Malware
8. SecuBox Labs
9. Virusign
10. VirusShare
11. TheZoo /Malware DB
12. ZeuS Tracker
13. MalwareBazaar