IP制限もしくはDigest認証
.htaccess
AuthUserFile /var/www/conf/.digestpass AuthGroupFile /dev/null AuthName "Digest Auth" AuthType Digest Require valid-user Satisfy any Order deny,allow Allow from xxx.xxx.xxx.xxx Deny from all
AuthUserFile /var/www/conf/.digestpass AuthGroupFile /dev/null AuthName "Digest Auth" AuthType Digest Require valid-user Satisfy any Order deny,allow Allow from xxx.xxx.xxx.xxx Deny from all