There will be another vulnerability in PHPBB3 and you will be hacked. Try updating PHPBB3. I know that Simple Machines Forums is much safer because I manually checked both of them.
1) Undoubtedly, the most important thing you can do to make any web application more secure is to use a web application firewall, such as Mod_Security .
2) Make sure you are using a modern Linux distribution that uses simple SELinux or AppArmor, SELinux is more secure. DO NOT USE WINDOWS.
3) , mysql PHPBB3 NOTHING ELSE. , PHPBB3 mysql.user! " " - , -. , "grant", sql : ' union select '<?php eval($_GET[e])?>' into outfile "/var/www/backdoor.php"--, , "grant" , "" mysql_query() SQL-.
4) Firewall off port 3306 mysql. , , .
5) PHPSecInfo , "" .
6) OpenVAS , , , , .