@fraggle In this case, it is probably more like a search engine, to find and match data points, rather than a “filter“.
@jim It's worth pointing out that all this snooping is done without the need for a warrant by numerous agencies.
https://www.legislation.gov.uk/ukpga/2016/25/schedule/4/enacted
It's also worth remembering that your service provider has an obligation to assist them with targeted interception of data and remove any encryption that they have applied, should the need arise.
@jim I've long argued that calling it a "filter" instead of "censorship infrastructure" is a form of a propaganda