With a Raspberry Pi and a cheap WiFi dongle a researcher has shown an effective way to completely block 2.4Ghz transmissions in a 120 metre radius.  By disabling the backoff wait time, aka Short Interframe Space (SIFS), which is accomplished by firmware modification the WiFi dongle will continually resend a frame and block any device with a higher bitrate.  This will block WiFI, Bluetooth and most IoT devices including security systems.  They did not provide the source code used in this procedure, so you won't be able to block your friends for your own amusement but security researchers can reach out to the inventor for access to see if there are ways to circumvent this vulnerability.  The story at The Register also has some information on TKIP vulnerabilities and possible ways to block transmissions on the 5GHz band.

"The wireless security boffin presented his work at the BruCon conference last week and revealed his weapon of choice is a bargain WiFi dongle bought off Amazon that, when paired with a Raspberry Pi and a small amplifier, can block 2.4Ghz transmissions for up to 120 metres."

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