Ahh, the question for the ages. I've seen the moderators refer this question many times to the
installation instuctions, which include a link to moving and renaming the Access MDB.
If you use the Access version, making that Access MDB inaccessible is critical. If the MDB is in a folder that can be accessed directly by a web browser, the MDB as a file can easily be downloaded and then opened locally in MS Access. If you can't put the MDB in a folder above your web root, you should assume a hacker can download it at will and you need to seriously look for a better host. You could use a username and password on the MDB, but Access security is notoriously weak and pointless for keeping a semi-savvy hacker out.
For better security, pay for an MS SQL hosting plan.
But that's just the first line of defense to protect the basic integrity of the database. After that you have to make sure you're using the most secure ASP code. Remember that hackers are always looking for holes so you have to check regularly for code updates.
Use extreme caution when changing the default forum settings, especially the types of files users are allowed to upload. If a hacker can upload his own ASP file, your entire site is wide open for all sorts of hacker fun.
Adjust folder security so that web users have Read-Only access to all folders except the folders for the Access MDB and uploads.
And last, the only thing that will save you from the worst disaster that can happen is the acceptance that a hacker WILL eventually break in and destroy everything you've done. WHEN a hacker hits your site, the only protection will be a good and frequent backup.