Description

This policy identifies Google GCE Networks that have Firewall Rules allowing unrestricted incoming traffic (0.0.0.0/0) from the internet to the standard FTP ports: TCP/20 (data) and TCP/21 (control).

In GCP, Firewall Rules are defined at the VPC Network level. Each rule either allows or denies traffic based on its configuration. These configurations specify the type of traffic (e.g., protocols and ports) and the source or destination (e.g., IP addresses, subnets, and instances).

Rationale

File Transfer Protocol (FTP) is a legacy protocol that transmits data, including usernames and passwords, in cleartext. Exposing FTP servers to the public internet creates significant security risks, including credential theft via network sniffing, brute-force attacks, and unauthorized access. Such exposure can result in data exfiltration, unauthorized file uploads, or compromise of internal resources.

Impact

All FTP connections from outside the affected VPC(s) can be blocked. If there is a legitimate business requirement for remote access, specific trusted source IP addresses should be explicitly defined in firewall rules to whitelist access only to the required FTP ports.

Audit

This policy flags a Google GCE Network as INCOMPLIANT if it includes at least one Firewall Rule that meets all of the following conditions:

• Source Ranges is 0.0.0.0/0 or ::/0
• Direction is INGRESS
• Allowed Protocols / Ports JSON specifies the tcp protocol and includes either 20 or 21 in the startPort - endPort range.