Security alerts from the Microsoft Office Trust Center appear when you open your presentation or click certain content in your presentation.
Your presentation contains content that might not be secure (for example, an executable file or a macro). By design, the Trust Center checks all files that might not be secure and displays a security alert.
If you don't want a file to be checked by the Trust Center while you deliver your presentation, before your audience arrives, move your presentation to a trusted location on the computer on which you plan to deliver your presentation.
To view the computer's current security and privacy settings in the Trust Center, see View my security settings in the Trust Center.
To move your presentation to a trusted location, see Add, remove, or change a trusted location.
To maintain a protective level of security, move your presentation to a trusted location instead of changing the default Trust Center settings to a less safe security setting.
You can use Presenter view to prevent security alerts from appearing where your audience can see them. Security alerts appear on the presenter's computer screen, but not on the projector (or screen) that the audience sees. To enable Presenter view in PowerPoint, see View your speaker notes privately while delivering a presentation on multiple monitors.