How to intercept incoming HTTP traffic and modify it?

Question

Computer networks

I need to replace a couple of words in the incoming traffic. And in the outgoing return them back.
I ran ettercap following the example from the article ( www.irongeek.com/i.php?page=security/ettercapfilter ), the program displays messages, but does not make any replacements. Moreover, not only I faced such a problem ( https://forums.hak5.org/index.php?/topic/29527-ett... ).
I'm trying to figure out how to solve a similar question ( How easy is it to replace raw TCP traffic (CentOS)? ), but I don't understand how to properly configure iptables.
Can anyone suggest how to solve this problem?
OS: Ubuntu 15.10
PS A browser extension might work too, because eventually you need to replace words on a web page.

Answer 1

https://github.com/Ettercap/ettercap/issues/715
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