Methods provide the highest leverage if you “own” the common element used across the most system components ie the lowest common denominator.

Saying it another way, don’t attack platforms, tools and channels, attack protocols since they are used across platforms, tools and channels

To this end, some examples:

Attack on

1) encryption - RSA backdoor

https://blog.cloudflare.com/how-the-nsa-may-have-put-a-backd...

2) hardware - Processor Backdoor

https://forums.whonix.org/t/expert-claims-nsa-has-backdoors-...

(this link is specifically great for this subject as it lists more than 10 different attack / compromise programs that are being run - with quite a few of them being protocol attacks - in the comments section )

3) networking - network gear firmware backdoor

https://www.cisa.gov/news-events/cybersecurity-advisories/aa...