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Description

Network security groups should be periodically evaluated for port misconfigurations. Where certain ports and protocols may be exposed to the Internet, they should be evaluated for necessity and restricted wherever they are not explicitly required.

Rationale​

The potential security problem with using SSH over the Internet is that attackers can use various brute force techniques to gain access to Azure Virtual Machines. Once the attackers gain access, they can use a virtual machine as a launch point for compromising other machines on the Azure Virtual Network or even attack networked devices outside of Azure.

Audit​

This policy flagged an Azure Network Security Group as INCOMPLIANT if it contains at least one Inbound Security Rule that meets all of the following conditions:

  • Direction is Inbound.
  • Access is Allow.
  • Protocol is either Tcp, Udp, *, or null.
  • Source Address Prefix is either Internet, * 0.0.0.0, /0, or Any.
  • Destination Port is 22.

If the Direction, Access, Protocol, or Source Address Prefix fields do not match the criteria above, the VM is marked as INAPPLICABLE.

If the Destination Port does not match, the VM is considered COMPLIANT.