Prevent any injection attacks Security Pro
http://addons.oscommerce.com/info/5752
Monitor sites for unauthorised changes with SiteMonitor
http://addons.oscommerce.com/info/4441
Block elicit access attempts with IP trap
http://addons.oscommerce.com/info/5914
htaccess protection
http://addons.oscommerce.com/info/6066
Cross Site Scripting attacks with Anti XSS
http://addons.oscommerce.com/info/6044
Make sure that all files, except for the two configure.php files have permissions no higher than 644.
Permissions on folders should be no higher than 755.
http://addons.oscommerce.com/info/6134 to assist with permission settings.