A fence, trusted staff on site, limited internal networks that are not connected to the outside world works well and are not that expensive.
But that wont get a cyber security contract long term to "fix" the system after every expensive logged intrusion.
The new networks have one good plus, wealth creation for the support, upgrade aspect.

So one cheap engineer can watch diverse networks rather than a vast unionized on site workforce per shift, every shift.
In the past low skilled staff would have to be in place, drive to or be on site 24/7.
The cost savings add up for the brand but the quality of the network installed expected correct commands on a private network not a network open to the world.
Years later all the limited networks open to the "net" per nation have been transversed and studied by a long list of people and other nations.
The "why" was to get costs down and remove staff while staying compliant with less on site experts.
It works but for the "internet" been allowed in as part of the trusted network.

Cyber-attacks, cyberspace are just a fancy way for wealthy US contractors to get more/new no bid funding and enjoy decades of wealth creation with new terms and sales.
It depends how a nations understands its strengths.
The US hopes the other side will always have a cell/sat phone, voice print, home computer, travel, be in CCTV range.
That political leaders can be contacted and make coup offers or let US "advisers" enter ie
https://en.wikipedia.org/wiki/Timeline_of_United_States_military_operations
The Soviet Union, East Germany would study the outside life of the mil/gov staff members of interest and look for lifestyle choices that would make then open to some interaction or create their own Western staff over decades.
Once established a turned person can stay in place for years, even selecting projects.
The UK perfected both technical and human options thanks to its skill sets needed in Ireland and tracking all Irish funding from the US.
Whats the best small nation, low cost system? GCHQ, MI6, SAS. That gives a nation the broad digital propaganda narrative, with that perfect personal covert in country touch when needed.
Re the submissions "Few would argue that cyber-attacks are not prevalent in cyberspace."
What is cyberspace to a nation, cult, faith, idea, flag? Propaganda, shills, sock puppets have to actually know what they are doing pre culture, pre coup.
Most nations and their wider, educated diasporas are very resistant to such "cyber" efforts. Color revolutions with outside funding soon fail.

Yes looking up from a home setting AC? Or down the grid (HVDC). https://en.wikipedia.org/wiki/... and https://en.wikipedia.org/wiki/...
The DC air conditioner might still be interesting with a savings % on site for solar been more direct and less AC to DC conversion loss.

Re "On a more serious note, what are the benefits/costs of using AC over DC in the home?"
AC gives you the national grid, hydro, power stations and epic scale.
DC gives a solar setup one less DC to AC to DC loss conversion to get the same result in the home setting (lots of roof panels, sun, short DC wire length to correctly sized air con unit).
Re: Do modern TVs run on AC, or are they just converting it to DC internally as well?
A boat, RV or truck shop can help with a list of DV 12v and 24v devices. Wire thickness, length, amps, devices used, storage then gets to be interesting design cost in the home setting.
With AC within reason any electrician can give you a great deal of "power" from the grid, 24/7 per room. With DC the length, width, usage, voltage math starts to get more interesting per device added.

Yes, found your own brand or ensure you are indispensable within a huge brand. Long shifts, constant reports, just in time repairs, solutions, over time.
If the company is getting a lot of no bid government work why change the system? Thats years of quality pay for running around trying to keep the contracts, working with consultants, networking, making friends..

Yes NSA and CIA are globally active with their own staff from other nations working on shared projects, cleared for NSA and CIA work, vaults, papers, files, networks.
The NSA has it collection systems, the CIA has its own vast duplicated networks.
That is not on some open, random, unencrypted, English searchable database in the USA waiting for any internal or external search request.
Very few nations keep any data in any readable form that can walk. East Germany lost its list of trusted staff to the West and ensured it never had an easy to find list until it went digital and the CIA got the final staff list. Switzerland lost its under mountain project/location of structures list.
The only searchable, English, plain text list that exist are bait, traps, honeypot, limited hangouts. Or lists of staff that are understood to have been in public, are are listed in other roles, front companies, web 2.0 stories, fake SS numbers, fake histories.

Honeypot of staff after 2000 with every name in English, project names on the same database, letters about how well a project went and the staff who worked on them all searchable. Just waiting to be read by any internal or external staff member with access or who could get access...
Its just a lot of useful cutouts, web 2.0 names, bait, front companies, names, terms, funding, locations that might have existed to push staff and products into US operations and bases after 2000.
If the US needed a deep cover mission for a fancy international NGO, a staff member can be located on their post 2000 work. The readable, open, contractor database can be looked into and Bob or Sally is found with a few years of work for the US mil or gov as their job application shows, with a SS number and other background.
Such a list also keeps all post 2000 contractors distant from all other US mil and gov staff going back decades.
Staff that have had war time experiences, talked to too many translators, made dual citizen friends under the stress of occupations, been friends with other nations staff, other nations embassy workers and contractors.

Every nation that thought it turned some cleared US staff since 2000 now understands that name is on a plain text list with on an open network. Who or what did they really get?
Sometimes unencrypted, network facing and plain text has its own long term value for other longer term honeypot missions.
Staff in the US used that huge easy to read database everyday, got to look up and enter names. Great to watch who was searching for what terms, names over years. Sensitive information is kept very secure AC, other bulk readable information is left to be found, internally and for others.

The US just lost its after 2000 plain text list of contractors and their letters of commendations/projects in an open network facing database.
How secure would the AI communications code be if that is the past standard of US network security?

Thats easy to do with a Tailored Access Operations unit like hardware upgrade to all exported systems to a nation or front company over many years and upgrades.
All computers arrives ready for collection as installed by default. For admin staff or the more secure communications room. Just waiting for an alternative network day, weeks, months later after local install and site testing.

An embassy site or massive gov building might open to visitors, cleaning contractors, new staff, insiders with faith or cult like foreign loyalties, people offering products for demo or sale, tours, public requests within that magic air gap distance thats not miles on a classic mil base but down to floors or 100's of feet.
The classic secure communications room might be very secure to trusted staff only but the wider network might be very leaky over 10's-100 of feet beyond physical security.
Physical access vs site access has always been the magic that so few designers understood. The network outside the building was 100% safe. At the next room distance plain text recovery was still an option.