Lately I am having trouble with my wireless dropping connections at
certain period of the day to the point I basically loose my connection
completely.

In my log files I found that every time it happens my Ubuntu is flooded
with hundreds of packets reported as follows:

"... kernel: [ 3033.724000] CCMP: received packet without ExtIV flag from
mac_address_here".

The packets arrive every second for a long period of time and disrupt my
wireless completely.

There are always the same 2 MAC addresses from which the packages get
in. The MACs belong to wireless clients in my neighbourhood.

The only "cure" to it so far found was to change my router AP operating
channel. This helps but not for a long.

I've tried to filter these MACs on my router AP. So, far one of them
have been stopped, but from another one I keep getting the packages. It
looks like my laptop card intercepting them directly. (?)

I have two questions about it.

First, is it just unintentional interference, or it could be an
indication of intentional attempts to brake into my network?

The reason I get suspicion here is that neither of these MACs never
operate on the same channel I do. E.g. today my AP was operating on
channel 9 and those guys on channel 6 and 11 respectively.

Second, what can I actually do about it, if filtering MACs on my router
AP did not stop these packages?

Any suggestions, please?