The two most common ways are research into the ownership of the news outlet, and by provenance tracking stories from known Russian-owned sites to other outlets. That's combined with old-fashioned journalism, where people attempt to verify suspected propaganda stories by finding corroborating evidence. (Sometimes the Russian sites run true stories, after all.)
This approach tends to produce some false positives, as there are news sites that don't fact check stuff before repeating it, and they end up being indistinguishable from state-sponsored propaganda to outside observers. I'm not sure how much it matters in practice if sites that routinely publish incorrect stories accidentally get misclassified.
> The two most common ways are research into the ownership of the news outlet, and by provenance tracking stories from known Russian-owned sites to other outlets. That's combined with old-fashioned journalism, where people attempt to verify suspected propaganda stories by finding corroborating evidence. (Sometimes the Russian sites run true stories, after all.)
Who is it that performs this service? And do all search engines consume the same classifications?
Considering how much obvious propaganda from Western sources I consume on a daily basis, I'm more than a little skeptical that they can be trusted to label what is and is not true from geopolitical rivals.
