This post will list four key source material describing how nation-state actors are working against western countries.
1. Wired magazine article from 2017. This is just one of many articles like it that came out as social media giants testified to the Senate Intelligence Committee in relation to Russian interference in the 2016 elections.
https://www.wired.com/story/six-revealing-moments-from-the-second-day-of-russia-hearings/
If it won't let you see the page, try incognito mode.
Russia has run an agency called Internet Research Agency, to run troll accounts on social media, among who knows what else. This information is now six years old. They have likely branched out.
2. Smarter Every Day YouTuber (who reveals he has been working for "Army Test Evaluation Command" ) interviews US General Robert Brown about multi-domain warfare. The Internet is the latest domain. The General appears at 11:22. This was posted in 2019:
Major cyber attacks have been happening in areas like petroleum industry in multiple countries.
3. British PM Theresa May described election interference and fake news from Russia in 2017:
https://www.theguardian.com/politics/2017/nov/13/theresa-may-accuses-russia-of-interfering-in-elections-and-fake-news
4. Examples of agents that are caught, is likely a thimble in comparison to the total.
Example of a Russian agent in the USA. The reason for deportation is purely technical. If you want to influence a country this way, you need to register first. She was not registered. She was involved in influencing the gun lobby among other things.
https://www.theguardian.com/us-news/2018/dec/10/maria-butina-russian-agent-nra-kremlin-infiltrate-plead-guilty
How many more are not noticed? Maybe they hide in academia?
https://www.theguardian.com/world/2022/oct/28/russian-spy-norway-canada-brazil-academic
What else is out there? How might they anonymously instigate extreme positions in various issues like Oil protests, Gaza protests, Sexual Identity and any kind of anti-government protest?
I've pinpointed some examples of Russian influence, but the same can be found from Iran and China.