problem with another strange hotspot connected to my network

hi

this is my network

adsl router ---- mikrotik pc v4.16 ---- accesspoint picostation

my problem : some one is connected to my picostaion with mikrotik pc and did setup hotspt and the login.html of his hotspot is just white page containng this word " your pc hase been hacked "

and my client always getting this page

i did block this mac from picostation access list

but it connected again with another mac of clients ap

and blocked this mac address again

and again it connected with another mac of ap of one of my clients

sorry friends for my bad english

i really need help

Go search the ubnt forums, there is a thread about an exploit with ubnt and firmware below 5.3.5. You will find info to remove the malicious code from your device.