> For the complete documentation index, see [llms.txt](https://cortex-docs.paloaltonetworks.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://cortex-docs.paloaltonetworks.com/analytics-alerts/alerts-by-name/external-user-call-via-microsoft-teams.md).

# External user call via Microsoft Teams

### Synopsis

| Field                | Value                                         |
| -------------------- | --------------------------------------------- |
| Activation Period    | 14 Days                                       |
| Training Period      | 30 Days                                       |
| Test Period          | 10 Minutes                                    |
| Deduplication Period | 1 Day                                         |
| Required Data        | Office 365 Audit                              |
| Detection Modules    | Identity Threat Module, SaaS Threat Detection |
| Detector Tags        | Microsoft Teams                               |
| ATT\&CK Tactic       | Initial Access (TA0001)                       |
| ATT\&CK Technique    | Phishing: Spearphishing Voice (T1566.004)     |
| Severity             | Informational                                 |

### Description

An external user called a user in the organization via Microsoft Teams.

### Attacker's Goals

Attackers may leverage Microsoft Teams to conduct voice phishing attacks by exploiting trusted communication channels with users inside the organization.

### Investigative actions

* Confirm that the external tenant and external user are authorized to call users in the organization.
* Check external domain reputation.
* Follow further actions performed by the user who participated in the call.
* Verify if the user account was compromised or was a victim of a voice phishing campaign.

### Variations

<details>

<summary>A first seen external user with a suspicious name initiated a Microsoft Teams call</summary>

**Synopsis**

| Field             | Value                                     |
| ----------------- | ----------------------------------------- |
| ATT\&CK Tactic    | Initial Access (TA0001)                   |
| ATT\&CK Technique | Phishing: Spearphishing Voice (T1566.004) |
| Severity          | Medium                                    |

**Description**

A first seen external user with a suspicious name successfully called via Microsoft Teams a user in the organization.

**Attacker's Goals**

Attackers may leverage Microsoft Teams to conduct voice phishing attacks by exploiting trusted communication channels with users inside the organization.

**Investigative actions**

* Confirm that the external tenant and external user are authorized to call users in the organization.
* Check external domain reputation.
* Follow further actions performed by the user who participated in the call.
* Verify if the user account was compromised or was a victim of a voice phishing campaign.

</details>

<details>

<summary>An external user with a suspicious name initiated a Microsoft Teams call</summary>

**Synopsis**

| Field             | Value                                     |
| ----------------- | ----------------------------------------- |
| ATT\&CK Tactic    | Initial Access (TA0001)                   |
| ATT\&CK Technique | Phishing: Spearphishing Voice (T1566.004) |
| Severity          | Low                                       |

**Description**

An external user with a suspicious name called via Microsoft Teams a user in the organization.

**Attacker's Goals**

Attackers may leverage Microsoft Teams to conduct voice phishing attacks by exploiting trusted communication channels with users inside the organization.

**Investigative actions**

* Confirm that the external tenant and external user are authorized to call users in the organization.
* Check external domain reputation.
* Follow further actions performed by the user who participated in the call.
* Verify if the user account was compromised or was a victim of a voice phishing campaign.

</details>


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