I've had some hackers try to get some of my other sites and I was wondering if any security plugins work best for a multisite setup?

I checked out
kareebu Secure or maybe PHP Anti-Hacker Component by OSE

if you have any other suggestions that would be great.

I don't know in detail all the secured extension.
I can just add to your list rsfirewall that i have saw several times used customer for whom I did billable support.

Edwin,

do you know if i can enable system lockdown in rsfirewall? or will that look for changes jms has made? I enabled the firewall, and brute force functions but i told rsfirewall to exclude all the jms components from the scans.

Thanks

I don't know.
I can just to tell you to test it yourself.
I can just tell you that RSFirewall is an extension defined for the JMS Tool and that you can install it.

Edwin, I think I have come across a bug with the RSFirewall! and Multisites... Right now if I uninstall RSFirewall! from any of my slave sites, their public page displays the following error message:

Warning: Invalid argument supplied for foreach() in /home1/dataload/public_html/<insertHostSiteFolder>/administrator/components/com_rsfirewall/helpers/rsfirewall.php on line 28

I'm wandering if the host site with Multisites is unable to deliver non RSFirewall! code to a slave site that doesn't have RSFirewall! installed...?

If you have effectivelly uninstall RSFirewall in the slave you should not have any call to the RSFirewall component.

If you have such call, this is perhaps because you still have something installed.
How did you uninstall the RS-Firewall.
Check with the JMS Tools if you still have plugin insatlled for RS Firewall.
Perhaps you have just uninstalled the component and not also the plugin "system - RSFirewall".