I'm not personally aware of filters targeting Nitter instances significantly, but I'm aware of whitelisting only the top 10 million sites (blocking "undesired"

I'm not personally aware of filters targeting Nitter instances significantly, but I'm aware of whitelisting only the top 10 million sites (blocking "undesired" things of course) and manually asking IT if you are visiting a low-traffic site. This stops a lot of phishing attacks but at the same time only allowing ~9.5 million sites is still too small.