Sharing SMB via Internet

So I went to the official sysinternals site the other day, and found a link to a network share with all the tools. I curiously entered it in my run window and the share appeared. I copied the tools I needed.

Now:

1. I wonder - was it some Microsoft hack to allow using SMB via internet? I always thought that SMB is only local

2. Was I compromised? I mean is SMB encrypted? Could anyone inject anything or override the share to a malicious one?

Also found it but it seems incorrect: https://www.reddit.com/r/HomeNetworking/comments/15uvaa0/how_can_i_create_a_smb_share_that_i_can_access/