> 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/unusual-sender-ip-subnet.md).

# Unusual sender IP subnet

### Synopsis

| Field                | Value                                         |
| -------------------- | --------------------------------------------- |
| Activation Period    | 14 Days                                       |
| Training Period      | 30 Days                                       |
| Test Period          | N/A (single event)                            |
| Deduplication Period | 1 Day                                         |
| Required Data        | Microsoft 365 Emails                          |
| Detection Modules    | Email                                         |
| Detector Tags        | Spoofing                                      |
| ATT\&CK Tactic       | Stealth (TA0005)                              |
| ATT\&CK Technique    | Social Engineering: Impersonation (T1684.001) |
| Severity             | Informational                                 |

### Description

This IP address has not been observed in correlation with the sender's fully qualified domain name within the last 30 days.

### Attacker's Goals

Disguise the email's origin by spoofing the received header to appear as a trusted sender, impersonating a trusted source, aims to mislead recipients into disclosing private data or performing unsafe acts.

### Investigative actions

* Review the email's received headers, to trace its path and spot spoofing signs.
* Examine the sender's IP address and domain reputation.
* Closely inspect the email content for malicious links, attachments, or requests for sensitive information.
* Monitor further actions taken, such as file downloads or access to potentially malicious links.

### Variations

<details>

<summary>Unusual sender IP subnet associated with infrastructure or tunneling services</summary>

**Synopsis**

| Field             | Value                                         |
| ----------------- | --------------------------------------------- |
| ATT\&CK Tactic    | Stealth (TA0005)                              |
| ATT\&CK Technique | Social Engineering: Impersonation (T1684.001) |
| Severity          | Informational                                 |

**Description**

This IP address has not been observed in correlation with the sender's fully qualified domain name within the last 30 days.

**Attacker's Goals**

Disguise the email's origin by spoofing the received header to appear as a trusted sender, impersonating a trusted source, aims to mislead recipients into disclosing private data or performing unsafe acts.

**Investigative actions**

* Review the email's received headers, to trace its path and spot spoofing signs.
* Examine the sender's IP address and domain reputation.
* Closely inspect the email content for malicious links, attachments, or requests for sensitive information.
* Monitor further actions taken, such as file downloads or access to potentially malicious links.

</details>

<details>

<summary>Unusual sender IP subnet associated with internal sender</summary>

**Synopsis**

| Field             | Value                                         |
| ----------------- | --------------------------------------------- |
| ATT\&CK Tactic    | Stealth (TA0005)                              |
| ATT\&CK Technique | Social Engineering: Impersonation (T1684.001) |
| Severity          | Informational                                 |

**Description**

This IP address has not been observed in correlation with the sender's fully qualified domain name within the last 30 days.

**Attacker's Goals**

Disguise the email's origin by spoofing the received header to appear as a trusted sender, impersonating a trusted source, aims to mislead recipients into disclosing private data or performing unsafe acts.

**Investigative actions**

* Review the email's received headers, to trace its path and spot spoofing signs.
* Examine the sender's IP address and domain reputation.
* Closely inspect the email content for malicious links, attachments, or requests for sensitive information.
* Monitor further actions taken, such as file downloads or access to potentially malicious links.

</details>


---

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