Since 14 July 2015, Microsoft has ended the support for Windows Server 2003. This means that the company will no longer provide patches, security updates, and security bulletins. As already happened for Windows XP, the repercussions under security perspective are serious because any security vulnerability that will be discovered in the future will remain unpatched leaving the system open to cyber attacks. According to a survey published by Spiceworks, 37% of the companies surveyed hadnt migrated to a newer OS, of those organizations 8% had no plans to migrate.”]
Source: http://securityaffairs.co/wordpress/38626/security/windows-server-2003-end-support.html