> 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 | Defense Evasion (TA0005) |
| ATT\&CK Technique | Impersonation (T1656) |
| 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
Unusual sender IP subnet associated with infrastructure or tunneling services
**Synopsis**
| Field | Value |
| ----------------- | ------------------------ |
| ATT\&CK Tactic | Defense Evasion (TA0005) |
| ATT\&CK Technique | Impersonation (T1656) |
| 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.
Unusual sender IP subnet associated with internal sender
**Synopsis**
| Field | Value |
| ----------------- | ------------------------ |
| ATT\&CK Tactic | Defense Evasion (TA0005) |
| ATT\&CK Technique | Impersonation (T1656) |
| 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.
---
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