Ensure that UDP Services are restricted from the Internet

Description:

Disable Internet exposed UDP ports on network security groups.

Rationale:

The potential security problem with broadly exposing UDP services over the Internet is that attackers can use DDoS amplification techniques to reflect spoofed UDP traffic from Azure Virtual Machines. The most common types of these attacks use exposed DNS, NTP, SSDP, SNMP, CLDAP and other UDP-based services as amplification source for disrupting services of other machines on the Azure Virtual Network or even attack networked devices outside of Azure.

Disable direct UDP access to your Azure Virtual Machines from the Internet. After direct UDP access from the Internet is disabled, you have other options you can use to access UDP based services running on these virtual machines:

Point-to-site VPN

Site-to-site VPN

ExpressRoute.