Almost none of it.

The amount of data flowing through undersea cables around the world is insane compared to the inter-satellite links available.

That being said, a lot of data that you use as a consumer on a daily basis doesn't pass through any undersea cable at all. It's more of a business problem than an individual problem.

The majority of the websites or online services you access are locally hosted on your own continent. Netflix, Facebook, Amazon, etc. all have local servers. Even for video games, most of the traffic is local just due to lag issues caused by too much distance.

What would break? Banking and financial institutions transferring money to or from overseas institutions to complete investments and loans ,Communications (Like e-mailing or calling a factory in China from the US, or contacting your Grandma in Thailand), International shipping, Flight tracking, etc.

While the satellites could take over for some of that, what would likely happen is specific companies would bid up the price for that limited capacity, and less financially valuable uses like being able to look at the latest lemmy posts from European submitters wouldn't work.

Russia can't take out all the "internet cables." Presuming we're talking about undersea cables, there are a fuckton of them. The logistics of taking out even a handful of those before the world takes action is beyond what Russia is capable of pulling off.

Even if they do manage to cut some, traffic would slow down, not stop. Then the cables would be repaired, and everyone would be more pissed at Russia than they already are.

It's nothing more than bluff and bluster. It would be a minor setback for the world, and have huge downsides to Russia.

It would give them (satellite internet providers) a boost if the cable cutting were continuosly occurring to a point of crippling then they may turn back the clock to what they have in military installations that's an Intranet a closed network but closed because they choose for it to be it doesn't actually have to be if they host large servers in areas that work on a local area connection (LAN) either and/or WIFI joined together and users connect to those servers to effectively use in effect a home made custom internet (Intranet) you could have frontend user interfaces to allow you pick and choose services or a search engine and or a file sharing server etc etc, you could even use banking apps just closed networked together, you could ramp that up by using large scale wifi and or satellite dish style relays or large antenna array equivelencies of such a thing capable of sending out the signal across an entire country and possibly beyond that..in fact theoretically it would be far safer to do that than having the current setup we usefor internet over undersea cables and so on in terms of outside access being denied, provided encryption was extremely high p2p end to end as well, it would be a case of if the owner says no then you don't get in unless they want you to, at that stage unless your in the country on site physically thre in person to incercept the transmitted data and break the code to access it, then you can't use it thus international countries cannot communicate or attack on it or inside of it and most certainly not entire building fulls of hackers any way, the serve3r providers would simply just transmit the data outbound to other countries as and when required not feed everything as in all communications through cables that every person can physically cut or attack out at sea or in some building in some on other continent it would prevent data being intercepted for the most part and lower infrastructure related hacks taking place and or working achieving success would be far lower than ever before. . The speeds would be confined to the relays speed and your connecting devices bandwidths as well so potentially ultra fast as well if the hardware improved further in time, that's alsio a way of loosing cables in ocean's for good doing that at the same time theoretically. It will not happen though, the world would say "enough's enough" before that stage of cable destruction were remotely possible to achieve by the Russian's