bettercap is a complete, modular, portable and easily extensible MITM tool and framework with every kind of diagnostic and offensive feature you could need in order to perform a man in the middle attack.

Version
Homepage https://www.bettercap.org/
GitHub https://github.com/evilsocket/bettercap
Code Documentation http://www.rubydoc.info/github/evilsocket/bettercap  
Author Simone Margaritelli (@evilsocket)
Twitter @bettercap
Copyleft Simone Margaritelli
License GPL v3.0 - (see LICENSE file)

Installation

Dependencies

All dependencies will be automatically installed through the RubyGems system but in some cases you might need to install some system dependency in order to make everything work.

On OSX (install brew and xcode tools first):

brew install libpcap

On Linux:

sudo apt-get install build-essential ruby-dev libpcap-dev net-tools

This should solve issues such as this one or this one.

Stable Release (RubyGems)

gem install bettercap

From Source

git clone https://github.com/evilsocket/bettercap
cd bettercap
gem build bettercap.gemspec
sudo gem install bettercap*.gem

Installation on Kali Linux

Kali Linux has bettercap packaged and added to the kali-rolling repositories. To install bettercap and all dependencies in one fell swoop on the latest version of Kali Linux:

apt-get update
apt-get dist-upgrade
apt-get install bettercap

Documentation and Examples

Please refer to the official website.