Hi, when I was looking at the DHCP client table in my router, I found an unknown android device. The router is provided by my ISP and have horrible wifi range, so I plugged it into my own wifi router, which shows up as the first IP address on the DHCP table ( 192.168.12.100 ), and has a constant expire time of 0:00:00. However, it also showed an android device with an expire time of 13 hours, which is odd because I have set the ISP router to ethernet routing and set the SSID to be hidden; also, I checked the DHCP table of my own router and all my devices are accounted for and the unknown device does not appear on it. I pushed the reset button on the ISP router, and now the DHCP table only shows my router, however, if I ping the address that the unknown android device had (192.168.12.101), I can still get a response, arp -a shows nothing, and if I type 192.168.12.101 into my browser, I get ERR CONNECTION REFUSED, instead of TIMED OUT when I tested 192.168.12.102 and up. The only other thing I have plugged into the ISP router is a powerlink, which does not connect to any android devices.
What is causing this? Could my wifi be hacked ( I reset all my routers and passwords about 15 days ago since i got paranoid from seeing an unknown appleTV option in airplay, and there are no appleTVs in the household)? I forgot to record the MAC address and the host name of the android device before I reset my ISP router, is there any way I can view it (Can still ping it, and chrome returns connection refused instead of timeout)?