What is skyrage malware : A new malware has been discovered, it infects other jars inside server folder (plugins, server jar...). The malware creates a service "vmd-gnu" to maintein a persistent access.
If you find: java.net.NoRouteToHostException: No route to host in your server logs probably you are infected.
You can use this command (from linux) to check if you are infected: grep -R "plugin-config.bin".