unlicensed radio frequencies is it secure for data communication link ??

I'm kind of new in the radio frequencies. so is it secure for data communication link (connecting 2 site offices 'business lan') together using free un-licensed radio frequency (ex 2.4/5/24G HZ) ?

assuming that i will use this link for just extending my connectivity (to other location) instead of using fiber(hard and cost effective), and I'm already implementing the security parameters in my own infrastructure(firewalls..etc)

example of the wireless products that I'm think of is 'Ubiquiti Nanostation NSM5, 5GHz'.

and kindly share with me if you have better soultions

Thanks alot