PSA: you can add mail aliases for outlook and set one of the new aliases as your only valid login address. That way no one knows your login email address in the first place.

What you need to realize is that for Microsoft, these attacks are constant. They deal with them basically 24/7/365. The target might change, but the attacks never stop.

Between Hotmail, Outlook, and exchange online (365) they're handling a large number of attacks per second all the time.

If they started to inform you about it, they would easily triple the emails they're handling due to all the failure messages.

This is nothing new to them, it's been going on since long before you noticed. Any MFA will effectively stop any attacker in their tracks. Make sure you have changed your password since you got that code sent to you, since that usually indicates a successful password breach.

Yubikeys are a good idea but you should always have a backup, so if you can afford it, buy two. One to carry, one to use. The downside is that each needs to be enrolled separately to each service that they're used for. It's not an issue to have multiple keys associated to the account, so that would be my recommendation.

I have a yubikey for work, and I use TOTP as a backup, and personally, I have a pair of Google Titan security keys. One to carry and one to stay at home.

Happened to me too yesterday. Gave me a big bump to my evening plans. Luckily I too have 2fa activated via 2 different systems {SMS AND second Mail address). They cracked my randomly generated password - which doesn't surprise me that much, brute force cracker are pretty effective nowadays.

What bums me is that I used this as an argument to teach a friend but he just used the same ol' reliable "naah, I'm too lazy". Can't change him, just told him to think about using 2fa everywhere money is involved. The rest is up to him.

What's also pretty bad from MS is that yes you can use several different mailadresses but no you can't prevent that all of them can be used as login. One is compromised but also used for mail traffic so I can't just delete it. But also can't prevent it from logging in to the account. Thanks MS..

This has been happening with my original MS email account for years. It's been in so many data breaches and pwns over the years that I basically have abandoned it. It's constantly being probed by malicious actors from outside the US. I still keep it for when family reaches out, otherwise I'd close the account.
There's no real way to block the attempts. Make sure your password is rock solid (randomize and store it in a password manager) and unique, put on 2FA, and ensure your recovery methods aren't easily phishable/leakable.

As long as you have 2Fa setup via a yubikey or phone app, and it via sms or email, you should be fine, they will give up eventually.

They cracked my password from a German VPN about a month ago. I Changed to passwordless within mins.

They seem to be really targeting Microsoft users, I am suprised Microsoft hasn't released a statement.

Someone hacked my account using an SMS exploit from Russia last week

You should enable passwordless auth with number matching.

did you report it?

Lol. I noticed an attempt every five minutes the other day. Joys of an older account. Use MFA everyone, it's getting hairy out there!

What I find hilarious is that Microsoft wants you to connect your entire digital existence to your Microsoft account… software keys, Windows license, Windows account/login, the works.

One little pwn and all that goes bye-bye.

Thanks, but no thanks. I’m still 100% local. I refuse to hook my Microsoft account into anything other than OneDrive, and even with that, I’m clipping all of it’s wings so that it shares only exactly what I want it to, and not all of my user directories.

As others pointed out, use the app to authenticate. I'm pretty sure this was happening to me about a month ago for about a week. Kept getting the approve and number notification for new login, but I would deny it. Eventually it stopped.