Avoid Everything Yahoo!
Should Yahoo be Blacklisted & all webmasters block their IP Ranges?
Already Done! Months ago I deleted my yahoo account as well as removing the yahoo search from all browsers.
Unfortunately I forgot my Flickr account .
Very old news, but all you can do is close your Yahoo accounts, links and search functions.
Webmasters blocking Yahoo IP ranges is pointless as the email service which "had" the rootkit does not browse websites.
It only affects people with Yahoo IDs that connect in to it. It does not work the other way round.
Yahoo is now owned by another company (https://verizon.yahoo.com), who if upholding the pre-existing deal with the NSA, are likely to also be doing it with all their other communication.
In which case now you need to block all Verizon, Yahoo and AOL IPs.
In the real world, millions of people are forced to use Yahoo because it is what their ISP has given them. British Telecom are the biggest UK ISP and have used Yahoo for many years, meaning that most of the UK has a Yahoo account they are forced to keep even if they don't use.