Have you had any recent encounters with UFOs, Unknown 2-Factor Occurrences?
If you receive a Microsoft Authenticator (2 Factor) Prompt to Approve a Sign-in on your Smartphone, and if you are Not sure the Authenticator Prompt to Approve was triggered by You or one of your Devices, then Not Approving is exactly the right thing to do!
Usually folks will configure Microsoft Authenticator to prompt users to Tap an Approval Prompt on their Smart Phones at a set time interval, say about every 30 - 60 Days.
Authenticator has a bit of an annoying Feature where in some scenarios it will Auto-magically attempt to Sign-in to verify you are still authorized to access your Microsoft Office 365 account, and are still the owner of the Device (Computer, Smartphone, Smart TV or Refrigerator, etc.).
If Authenticator's Timer hits the 30 - 60 Day Mark, and If one of your Computers or Devices is triggered to Sign-In, an Authenticator Prompt pops-up on your iPhone or Android Smartphone to Approve.
And, if the Computer that triggered the Authenticator Prompt is not within your Line-of-Sight or at Arm's Reach, then you may have no idea If it is really an annoying Legit Auto-magical Authenticator Prompt, or If the Authenticator Prompt was triggered by a Bad Guy that somehow discovered your Password. So, for situations like this, it is best to Not Approve.
If the Authenticator Prompt was Legit, and If you did not know that, Not Approving will cause No harm!
Typically, the Device or App that Triggered the Authenticator Prompt will immediately surrender and simply stop asking. And then typically sooner or later you will accidentally discover What Device was behind the Authenticator Prompt.
IF after denying (Not Approving a Sign-in) once, If you continue to Receive Repetitive Authenticator Prompts to Approve, or if Authenticator Prompts start to occur in rapid fire machine gun precision, and You have no idea who or what is doing the firing, then you Definitely should Not Approve and should Change your Password and/or immediately Contact your M365 admin or us.
If you are using your Computer or Smartphone when an Authenticator Prompt to Approve occurs, there is a very good chance it is from You, and that an App Window that Triggered the Authenticator Prompt is hiding behind the App Screen or Window you are currently staring (or glaring) at. For example, OneDrive auto-prompting for your Approval is a frequent suspect.
In today's world of cyber villains, you can't be too safe. When you encounter any UFO incidents where you are uncertain about the sighting, be sure to contact us and we will do a bit of research to determine if your case is a legit X-File!
PS: Multi-factor authentication (MFA) means you must provide more than one way to sign-in to Microsoft 365, and is one of the easiest ways to tightly secure your business. MFA is a Must to Block over 99% of account hack attacks!
Here are several References for you to learn more about Multi-Factor (2-Factor) Authentication and Microsoft Authenticator: