Shield allows you to protect elasticsearch data with a username and password. It provides additional functionalities like like encryption, role-based access control, IP filtering. It is Official Plugin of Elasticsearch which embeds well with other elasticsearch products like kibana and logstash. Initially Shield is available for 30days try after which you can renew the license

Installing ElasticSearch

sudo add-apt-repository ppa:webupd8team/java
sudo apt-get update
sudo apt-get -y install oracle-java8-installer
wget https://download.elastic.co/elasticsearch/elasticsearch/elasticsearch-2.3.2.deb
sudo dpkg -i elasticsearch-2.3.2.deb
sudo update-rc.d elasticsearch defaults 95 10

Setting up Shield

cd /usr/share/elasticsearch (ES_HOME Directory)
bin/plugin -i elasticsearch/license/latest
bin/plugin -i elasticsearch/shield/latest
service elasticsearch restart
bin/shield/esusers useradd <user-name> -p <password> -r <role-name>

Verifying shield:

curl -u <user-name>:<password>  localhost:9200