ORCA.103: Outbound spam filter policy settings configured.
| ID | ORCA.103 |
| Severity | Medium |
| Suite | ORCA |
| Product | Defender |
| Related products | Exchange Online |
| Feature | Anti-spam |
| Security area | Email and collaboration protection |
| Resource type | Policy |
| User impact of fixing | Low |
| Effort to fix | Low |
| Framework controls | nist-800-53-r5:SI-8 Spam Protection |
| MITRE ATT&CK | T1078.004, T1534 |
| Reads from | Exchange Online |
What this checks and how to fix it
Section titled “What this checks and how to fix it”Configure the maximum number of recipients that a user can send to, per hour for internal (RecipientLimitInternalPerHour) and external recipients (RecipientLimitExternalPerHour) and maximum number per day for outbound email. It is common, after an account compromise incident, for an attacker to use the account to generate spam and phish. Configuring the recommended values can reduce the impact, but also allows you to receive notifications when these thresholds have been reached.
Remediation action
Section titled “Remediation action”Set RecipientLimitExternalPerHour to 500, RecipientLimitInternalPerHour to 1000, and ActionWhenThresholdReached to block.
Related Links
Section titled “Related Links”- Microsoft 365 Defender Portal - Anti-spam settings
- Recommended settings for EOP and Microsoft Defender for Office 365 security
Mito check, based on ORCA. Author: soulemike. Open-source licences.
Open-source licences. CIS Benchmark material © Center for Internet Security, Inc.; CISA SCuBA baselines are public domain (CC0).
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