There is excellent free products like Antivirus for Linux from Comodo .
I suggest to extend it to be a complete shared hosting server security suite .
Also a solution for prevent outbound spamming .
Easy integration with shared hosting control panels like Plesk , Cpanel etc and support them.
Don’t force GUI and create web interface
Same features as above for Windows also .
With these features (and of course some others which currently i don’t remember) Comodo will be the only free suite in this area . I think the shared hosting servers are good target for you to spread your products .