If you prefer to have the sharepoint available on Internet, you probably prefer to encrypt traffic via SSL/HTTPS. Here is how below. The steps are more specifically for IIS6 and Sharepoint Server 2007.
After enabled SSL/HTTPS for the site under IIS 6, proceed following via Sharepoint central administration page:
Open Central Administration
Select Alternate Access Mappings
Now select Edit Public URL’s
Select the site you have put the certificate against in IIS from the Alternate Access Mapping Collection
Enter the address with https://… into the Public URL field.