When they ask “how did you hear about the position?”, the interviewer just wants to know if you’ve taken the time to research the company and if you have a genuine reason for wanting to talk with them. Mention a product, a mission statement on the website, a reputation for talented employees, or whatever else seems applicable to that specific company. Come up with a great reason. Don’t make it seem like they’re just one company among many. Or that you’re sending your resume out to them for no particular reason other than wanting a job.
Example: “I would say that as a security officer, I’m vigilant, proactive and committed to ensuring safe, secure, and orderly environments. In my last incident response rating, I received a 99% against the team average, which has been at around 97% over the past 3 years. I like to be thorough, documenting all incidents. I’m also a lifelong learner, always seeking out the latest security equipment and techniques to patrol buildings. I frequently make suggestions to management about security improvements and changes as my motivation comes from making a meaningful contribution.”
Any candidate can read and regurgitate the company’s “About” page. So, when interviewers ask this, they aren't necessarily trying to gauge whether you understand the mission—they want to know whether you care about it. Start with one line that shows you understand the company's goals, using a couple key words and phrases from the website, but then go on to make it personal. Say, “I’m personally drawn to this mission because…” or “I really believe in this approach because…” and share a personal example or two.