Sources

https://en.wikipedia.org/wiki/Social_engineering_%28security%29

https://www.itgovernance.co.uk/blog/real-life-examples-of-social-engineering-part-2/

https://www.scribd.com/document/172451706/A-Case-Study-in-Social-Engineering

https://www.getsafeonline.org/press/over-21-million-lost-to-social-engineering-scams-since-the-beginning-of-the/

https://www.social-engineer.org/social-engineering/social-engineering-infographic/

https://www.social-engineer.org/framework/attack-vectors/vishing/

http://resources.infosecinstitute.com/common-social-engineering-attacks/

https://solidmonster.files.wordpress.com/2014/01/frequency-of-different-security-attacks.png

https://digitalguardian.com/blog/2017-data-breach-report-finds-phishing-email-attacks-still-potent

http://www.verizonenterprise.com/verizon-insights-lab/dbir/2017/

https://phoenixts.com/blog/how-to-prevent-social-engineering-you-cant/