I suspect someone is stealing my Wi-Fi

Few days b4, my wifi password mysteriously changed. I contacted the customer service and they redirected me to my Router Configuration site. which is your default gateway ip address. And I changed my wifi pass. to my preference, also upgraded my security to WAP. theres a utility there where you can check who's using the wifi. they show the device name and its IP address. While wandering through all the things , I reverted back to "whos using the wi-fi" utility. and I found this (check the link). In the Device name and the IP address, it shows "ERROR", thats creepy (NexusSync is me), cuz no one excluding me was using the wifi. I quickly took a snapshot and disabled my router so that No more theft is done. First the mysterious password change, Now this. Please help.

Asked May 27, 2014
Disconnect all of your devices and find the IP of the thief. Block that local IP.
Answered May 27, 2014
Philantrophist - Did you even see the pic? I cant see the Ip add. nor the device name of the user, only Client ID is visible. And can wi-fi passwords change on its on. And when I go on my Firewall log in router config. site, I came across very recent SYN floods and Illegal TCP headers, what are they? can you get any clues from them. And for security , I usually turn off my Router when i'm not using my laptop so no theft is done.
Umm do you have any stalkers or people who mysteriously visit often?? From what I know password can't change on its own this has happend to my older sister but it turnd out it was her ex boyfriend crapping around with things or somthing I hope you find out who it is maybe somone hacked your account idk :(
Answered May 28, 2014
Umh, nope... Just a friend. Pretty honest and sensible (Also he doesn't live near me), I dont suspect my neighbours as they are mostly elders who don't know how to operate machinery.
No computer geek next door, So no possible suspect. The password change is seriously intriguing .
But Now, I think this situation is under-control as I usually check devices using my wi-fi and I find nothing suspicious. The nearest thing to a Clue, I have are the "SYN floods" and "Illegal TCP Headers", But I dont have the faintest idea about them. Co-incidence, That the game "Watch Dogs" Just released in my Region. (The Game is about Hacking, as well :P )
Hmmmm well I hope it's all good but the password change is whats bugging me I mean the error thing could be millions of reasons but the password change is really creeping me out 0-0 I hope it's nothing big :)
U could call some people to come and see what the illegal top headers is about maybe technicians? Or somone who's good at this technology stuff

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