One may find the following resources useful for measures on how to secure one's infrastructure:

- Security Guide: How to Protect Your Infrastructure Against the Basic Attacker [0]

- 7 Security Measures to Protect Your Servers [1]

[0] http://blog.mailgun.com/security-guide-basic-infrastructure-...

[1] https://www.digitalocean.com/community/tutorials/7-security-...