RC4 is a stream cipher that’s been used to encrypt plain text for many years, but security researchers have found many biases and have published attacks that can be used by hackers to decrypt the data. Thus the move to disable it by default, which Microsoft says it will do on Edge and IE running on Windows 7, 8.1 and 10 in early 2016. Mozilla plans to drop support when it releases v44 of Firefox and Google plans to do the same in January or February.
Read more here:
https://threatpost.com/google-mozilla-microsoft-to-sever-rc4-support-in-early-2016/114498/
