This was done in the 70s/80s, but I doubt it's worth the effort now. It only worked because the Soviets assumed the cables were inaccessible. End-to-end encryption is a thing even for the general public now.
It's very much still happening. Metadata is enough for intel purposes, storage is ridiculously cheap and post-quantum breaks of key exchange is forever 20 years away like fusion.
> "The traffic shown in the slides is now all encrypted and the work the NSA/GCHQ staff did on understanding it, ruined."
The third link is twenty years old, and no longer very doable for the same reasons as above. Anyone still sending unencrypted stuff along these cables deserves to get stung.
You're not gonna get any useful metadata out of it since the entire pipe is encrypted/decrypted at each end. All you'd see from tapping it at the middle is an unbelievably vast stream of random ones and zeros, the encrypted version of all commingled traffic.
It's very much still happening. Metadata is enough for intel purposes, storage is ridiculously cheap and post-quantum breaks of key exchange is forever 20 years away like fusion.
https://www.nytimes.com/2015/10/26/world/europe/russian-pres...
https://www.theatlantic.com/international/archive/2013/07/th...
https://www.zdnet.com/article/spy-agency-taps-into-undersea-...