It depends on some aspects of the protocols and implementations. NetBIOS/NetBEUI is not routable at all and it works sending broadcasts. Workgroups, domain joining, browsing, hostname update and other features of the SMB suite will be restricted to your network due those limitations. It shall work in a local network environment but not over TCP/IP. However, to overcome this issue, NBT (NetBIOS over TCP/IP) and WINS servers where implemented so, things like hostname updates could be done on larger networks where routing is needed.
SMB itself is just an upper-layer protocol (presentation & application), and it will consume lower-layer protocol (network, transport, session) services. It will work across networks, but it heavily depends on the implementation/version of SMB you are using, and the operating system.
The Good:
- It should work (in theory). Its just a matter of accessing the IP addresses where this share is published. Port redirection is probably needed on your modem or your firewall if you are "directly attached" to the Internet.
The Bad:
- SMB is not safe at all. VPNs' (IPSec, OpenVPN, PPTP ...) first purpose on this setup is to solve the encryption and security issues of the SMB protocol, not routing ones. Edit: Maybe another layer of security can be added with Server Signing with samba 3.3.x+
The Ugly:
- Your ISP could be blocking this kind of traffic (
445/tcp) - SMB does not have any kind of check-summing/verification, and it could have performance issuesperformance issues on high-latency networks.
tl,dr; It's better to use other protocols like WebDAV, sftp, scp or ftp.
