These people telling you to install htaccess are wrong. What it looks like happenned was that you were hacked, and someone is now using your server to store and serve something - almost certainly warez. Talk to your sysadmin, get them to change the passwords. Also, look through your directories and find what it is that is being stored.
Of course, you also should always have your content protected by htaccess.
Cheers,
Backov
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