Malicious clients/APs need much less energy to DoS a network Wi-Fi network. WPA3 adds optional PMF (802.11w) to protect against rogue deauth over WPA2. Also, not deploying 802.11r but deploying WPA-3 only mode and device/user cert-based 802.1x auth also help.
Sure, but compliant Wifi devices use miniscule transmit power. If you're a criminal you can easily hook up a car battery/generator to a 1000 W transmitter and cover a pretty wide area, or use a directional antenna to focus it a bit more on your target. These sorts of jammers definitely exist, too. Downside though is you're also lighting a huge beacon that says "HELLO I AM DOING SOMETHING ILLEGAL", so you will not be able to keep it up forever. Protocol-based attacks are more discrete, but newer APs (especially enterprise) have countermeasures.
I dunno how legit they are but a Google search finds examples claiming a 20 W jammer can cover 500 meters. I'm skeptical that's accurate but it's probably within an order of magnitude. Enough to cover a house, and a large transmitter would plausibly be able to block out a larger facility.
Adding a couple of thoughts I had while reading it:
- If the criminals' jamming only needs to protect their identity when people look at footage in the future (as opposed to taking offline a large facility's entire network of cameras so that security can't tell where the criminals are in real time) then they could potentially carry the jammer with them, in which case it just needs to be strong enough to block any camera within sight rather than the full building
- In addition to scaling the power of a jammer to take out a big enough area, they could place multiple jammers around the location, either to combine to a larger area or to expand on your directional antenna idea to target individual networked items (cameras, routers, whatever). Even if having many of them means there isn't time to collect them all again when leaving, assuming the crime's pay-off is significant then it could easily still be cost-effective to consider them single use jammers (I'm assuming it wouldn't be hard for people smart enough to plan this sort of crime to make sure that the left-behind jammers can't be traced back to them as an easy solve for the police).
Jammers also aren't super expensive and don't need to be supervised, it's entirely possible a thief could just leave a big one in a trash can or something and then abandon it.
All that said though I don't think this is a credible threat against anywhere with minimum legitimate security. Everything should be hardwired and battery backed up in any reasonable security system. It's mostly a thing that would effect cheap residential systems.
My guess would be that A is legal and B might not be, but I've never had reason to look up the relevant laws and I don't know if it would be the same in different countries either.
But yeah, I doubt most purchases of portable jammers are for legal use.
a) I've never been quite sure. People do testing in Faraday cages so there has to be some exception. I'm pretty sure as long as you aren't interfering externally and are being responsible nobody is gonna fine you.
What you can't do is operate a business and fill the lobby for example with jammers that wipe out cell phone service and then require people to pay for access via WiFi.
Ideally a well-designed camera would buffer locally when its WiFi path is down. But there's always limits there and I suppose if the criminal started the jamming a bit before entering line of sight, it should work. Then again I suppose most security cameras probably don't buffer at all or just barely enough to smooth out a network hiccup.