Regions that need to opt in for MFA telephony verification

As a protection for our customers, Microsoft doesn't automatically support telephony verification for certain region codes. If you want to receive traffic from phone numbers with these region codes, your administrator must submit a support ticket and request to opt in.

Why this protection is needed

In today's digital world, telecommunication services have become ingrained into our lives. But advancements come with a risk of fraudulent activities. International Revenue Share Fraud (IRSF) is a threat with severe financial implications that also makes using services more difficult. Let's look at IRSF fraud more in-depth.

IRSF is a type of telephony fraud where criminals exploit the billing system of telecommunication services providers to make profit for themselves. Bad actors gain unauthorized access to a telecommunication network and divert traffic to those networks to skim profit for every transaction that is sent to that network. To divert traffic, bad actors steal existing usernames and passwords, create new usernames and passwords, or try a host of other things to send text message messages and voice calls through their telecommunication network. Bad actors take advantage of multifactor authentication screens, which require a text message or voice call before a user can access their account. This activity causes exorbitant charges and makes services unreliable for our customers, causing downtime, and system errors.

Here's how an IRSF attack may happen:

1. A bad actor first gets premium rate phone numbers and registers them.
2. A bad actor uses automated scripts to request voice calls or text messages. The bad actor is colluding with number providers and the telecommunication network to drive more traffic to those services. The bad actor skims some of the profits of the increased traffic.
3. A bad actor will hop around different region codes to continue to drive traffic and make it hard for them to get caught.

The most common way to conduct IRSF is through an end-user experience that requires a two-factor authentication code. Bad actors add those premium rate phone numbers and pump traffic to them by requesting two-factor authentication codes. This activity results in revenue-skimming, and can lead to billions of dollars in loss.

IRSF poses a significant threat to online businesses and can cause reputational damage. By understanding IRSF, you can be more aware of the problem and can engage in implementing preventive measures such as regional restrictions, rate limiting, and phone number verification.

SMS verification

For SMS verification, the following region codes require an opt-in. This means that if you'd like to use telecom in these regions, you'll have to reach out to support.

Voice verification

For voice verification, the following region codes require an opt-in.

Region specific service limits

Next steps

• Understanding telephony fraud
• Authentication methods in Microsoft Entra ID