> 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/suspicious-sending-domain-with-sender-address-randomization.md).
# Suspicious sending domain with sender address randomization
### Synopsis
| Field | Value |
| -------------------- | ----------------------- |
| Activation Period | 14 Days |
| Training Period | 30 Days |
| Test Period | 30 Minutes |
| Deduplication Period | 1 Day |
| Required Data | Microsoft 365 Emails |
| Detection Modules | Email |
| Detector Tags | Phishing |
| ATT\&CK Tactic | Initial Access (TA0001) |
| ATT\&CK Technique | Phishing (T1566) |
| Severity | Informational |
### Description
Multiple messages from a single sender domain were observed over a short period, each using a unique sender address. This per-message sender randomization is uncommon for legitimate senders and suggests automated behavior.
### Attacker's Goals
Trick the user into clicking a link, while avoiding detection.
### Investigative actions
* Examine the sender's IP address and reputation.
* Verify whether the sender's IP address has appeared in different log sources before, and if it is recognizable.
* If the message contains attachments or links, scrutinize them for any suspicious indications.
* Monitor further actions taken, such as file downloads or access to potentially malicious links.
### Variations
High-volume sender domain with per-message sender randomization
**Synopsis**
| Field | Value |
| ----------------- | ----------------------- |
| ATT\&CK Tactic | Initial Access (TA0001) |
| ATT\&CK Technique | Phishing (T1566) |
| Severity | Informational |
**Description**
A high volume of emails was observed from a single sending domain over a short time period, each using a unique sender address. This high volume per-message sender randomization is uncommon for legitimate senders and suggests automated behavior.
**Attacker's Goals**
Trick the user into clicking a link, while avoiding detection.
**Investigative actions**
* Examine the sender's IP address and reputation.
* Verify whether the sender's IP address has appeared in different log sources before, and if it is recognizable.
* If the message contains attachments or links, scrutinize them for any suspicious indications.
* Monitor further actions taken, such as file downloads or access to potentially malicious links.
---
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