Hi Edwin how are you?

I am thinking in the security of my Multisites platform. I have configured all the ftp permissions as suggested by joomla but I want additional security. Do you have some special recommendations on this topic?
I have been thinking in buying this security component www.jfirewall.com
What do you think?
Do you think that protecting my mastersite domain would be enough or should I buy a licence for each slavesite domain?

Thankyou for your time, have a nice day.

First in term of license, you don't have to install JMS multisites in the slave site and you can also install it an unlimited number of times.

Concerning addition firewall product this can effectivelly increase the security and mainly to reduce risk of hacking your websites.

If you have put your master in a specific domain or subdomain with a specific directory, you can also add a htaccess with specific password in addition to the joomla password.

All actions to increase the security is welcome as you can never guarantee the 100% secure for any extension (whatever the extensions)

ok thankyou.