The surveillance agencies are arguably much more powerful now than they were in the 1970s given the massive increase in technology related to computers and electronic communications. The CIA and FBI had a massive program of attacking and subverting dissident groups in the US and instigating coups overseas during the Vietnam War. Here is a description of some of the tactics used in the US:
1. Create a negative public image for target groups (for example through surveilling activists and then releasing negative personal information to the public)
2. Break down internal organization by creating conflicts (for example, by having agents exacerbate racial tensions, or send anonymous letters to try to create conflicts)
3. Create dissension between groups (for example, by spreading rumors that other groups were stealing money)
4. Restrict access to public resources (for example, by pressuring non-profit organizations to cut off funding or material support)
5. Restrict the ability to organize protest (for example, through agents promoting violence against police during planning and at protests)
6. Restrict the ability of individuals to participate in group activities (for example, by character assassinations, false arrests, surveillance)
COINTELPRO - Wikipedia
What is the COINTEL program? Is it relevant today? - Outside The Beltway - Hannity Community
The surveillance capabilities have massively increased since then, and the COVID lockdowns have made unmonitored personal communication virtually impossible. Australia is a key part of the Five Eyes global surveillance alliance.
https://www.news.com.au/technology/online/hacking/snowden-leaks-five-eyes-alliance-australian-involvement-detailed/news-story/8c2755b952b54c147c7bf36b8413e83f
The era of the Church Committee report may be the last example of real civilian oversight over the CIA/FBI/NSA. Now the oversight appears to go the other way, the agencies and their related contractors monitor and control the elected governments and corporate media.