Where can I find free content filtering systems?

Question

Computer networks

Content filtering systems based on open source software . Where can these be found and are they available? I know the Internet censor, but for some reason the site does not work for them. We need only current ones. Thanks in advance!
PS for education.

Answer 1

if "for education" is for an educational institution, then this is possible . 800 rubles a year for the network is, IMHO, "free"