For Windows 10 see the following discussion that has some suggestions of things to check and configure on Windows 10. Things like ensuring NetBIOS over TCP/IP is enabled. Both the My Cloud and Windows PC’s use the same workgroup name.
As to the issue of network security or public access to the My Cloud. That is a larger discussion on security of one’s home network including router configuration and various potential security vulnerabilities of both the My Cloud and of other local network equipment.
Generally if one is using WiFi their traffic can potentially be intercepted and if one is determined enough they could possibly exploit certain vulnerabilities to crack that WiFi signal and get onto one’s encrypted WiFi network. Any time one allows a network device to have inbound remote access from the Internet they are opening up a potential exploit hole in their network. Generally one’s local network IP address is different than the public IP address of one’s local network. It is the local network router that uses a network address translation table to route permitted traffic from the public network (internet) to devices on your local network like the My Cloud.
How secure is the My Cloud from public hacking? That is debatable. One can at least set Shares to Private to limit and control access through the means of passwords for any user you grant access to the My Cloud, either publicly or on the local network.
Generally one should, regardless of the device, practice good security measures for sensitive data. If you don’t want your sensitive data to be hacked then don’t put it on a device that has (how ever remote) access to the internet or that others can potentially gain access to.
