Questions for computer security experts

I have next problem.

My neighbors from other apartments have a remote wireless access to my laptop and desktop PC and create me some problems and watch what I am doing.

They can connect to my computers when I don’t use Internet.

I have used different antivirus programs, firewalls, antispyware software, but all these programs haven’t found anything suspicious.

I suppose somebody has done something with my PC (for example, with motherboard, BIOS or installed a special hardware device). This person is very experience in computers and microelectronics.

When somebody connect to my laptop or desktop PC I watch as my program begin to work slower.

I think because my useful operation memory to become smaller.

Earlier I have done format HD and installed OS (Windows, Linux Ubuntu) and software again but this didn’t help me.

Maybe I must look for a device for scanning all frequency range that can use for remote wireless access?

Then I can jam so radio waves with another apparatus.

P.S. Excuse me for my English.

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