# Safe attachments unknown malware response set to block messages
When Safe attachments unknown malware response set to block, Microsoft Defender for Office 365 prevents current and future messages with detected malware…
Source: https://maester.dev/docs/tests/ORCA.124
Part of ORCA · Defender · Safe Attachments · All checks
```powershell title="Run this check"
Invoke-Maester -TestId ORCA.124
```
## Overview
When Safe attachments unknown malware response set to block, Microsoft Defender for Office 365 prevents current and future messages with detected malware from proceeding and sends messages to quarantine in Office 365.
#### Remediation action
Set Safe attachments unknown malware response to block messages.
#### Related Links
* [Microsoft 365 Defender Portal - Safe attachments](https://security.microsoft.com/safeattachmentv2)
* [Recommended settings for EOP and Microsoft Defender for Office 365 security](https://aka.ms/orca-atpp-docs-7)
## Details
Every attribute of this check
| Field | Value |
| --- | --- |
| Test ID | ORCA.124 |
| Severity | High |
| Suite | ORCA |
| Product | Defender |
| Related products | Exchange Online |
| Feature | Safe Attachments |
| Area | Email and collaboration protection |
| Resource type | Policy |
| User impact | Low |
| Implementation cost | Low |
| MITRE ATT&CK | T1566.001 Spearphishing Attachment, T1204.002 Malicious File |
| Supports controls | nist-800-53-r5:SI-3 |
| PowerShell test | [Test-ORCA124](https://github.com/maester365/maester/blob/main/tests/orca/Test.ORCA.124.ps1) |
| Services | ExchangeOnline |
| Compatible licenses | ATP_ENTERPRISE |
## Source
- Test: [`tests/orca/Test.ORCA.124.ps1`](https://github.com/maester365/maester/blob/main/tests/orca/Test.ORCA.124.ps1)
- Documentation: [`tests/orca/Test.ORCA.124.md`](https://github.com/maester365/maester/blob/main/tests/orca/Test.ORCA.124.md)
