TS, subukan mong gamitin yung WNetWatcher ni Nirsoft (portable Windows app), ini-scan nya yung Wi-Fi at nire-report lahat ng naka-connect, may chance na makita mo yung private mac address na ginagamit nila, at yun pwede mo nang i-black list:
www dot nirsoft dot net/utils/wireless_network_watcher.html
Alisin mo na lang yung mga spaces at palitan ng period yung dalawang dots. Pagka-download sa Windows, i-unzip mo lang sa isang folder at double click mo na yung WNetWatcher.exe.