External IP Vulnerability Scans

Last updated: December 23, 2025

External IP Vulnerability Scans are used to identify security exposures on internet-facing systems by scanning public IP addresses without using credentials. These scans simulate what an external attacker can see and access from the internet.

This article explains how External IP Vulnerability Scans work, what they detect, how they are executed, and their limitations.

What External IP Vulnerability Scans Do

External IP Vulnerability Scans evaluate publicly accessible services and systems exposed to the internet. The scan assesses only what is visible externally and does not require access to internal networks or credentials.

These scans are commonly used to:

  • Identify exposed services and open ports on public IP addresses

  • Detect vulnerable service versions through banner analysis

  • Assess external attack surface and perimeter exposure

  • Validate firewall rules and network segmentation

  • Identify unintended internet-exposed assets

Execution Model

  • Execution: Cyrisma cloud-based scanning service

  • Agent requirement: No local agent required

  • Credential usage: None

Scans are executed from Cyrisma-managed external infrastructure and target only publicly reachable IP addresses.

Firewall Allowlisting Requirements

To ensure External IP Vulnerability Scans can reach your public-facing assets, firewalls and network security controls must allow inbound scanning traffic from Cyrisma’s external scanning infrastructure.

External scans may originate from any of the following IP addresses, which should be allowlisted where inbound filtering is enforced:

3.16.88.2
3.130.94.37
3.132.30.96
3.149.173.97
3.150.35.86
3.150.79.210
18.223.219.71
18.224.112.97

If inbound traffic from these IP addresses is blocked, scan results may be incomplete or missing expected findings.

Prerequisites

To run External IP Vulnerability Scans:

  • The target IP address must be publicly routable

  • The IP must be reachable from the internet

  • Firewalls and security controls must allow inbound traffic from Cyrisma scanning IPs

No agent deployment or credential configuration is required.

Data Collected

External IP Vulnerability Scans collect externally visible information only, including:

  • Open TCP and UDP ports

  • Detected services and protocol versions

  • Service banners and fingerprints

  • Operating system guesses based on network fingerprinting

  • Publicly exposed web services or network endpoints

  • SSL/TLS configuration and certificate details

  • Banner-identified CVEs and known exposure indicators

The scan does not access internal system configuration or file systems.

Accuracy Considerations

External IP scans provide a realistic attacker-view assessment but have inherent limitations:

  • Results are based on what is externally visible

  • Vulnerabilities requiring authentication cannot be detected

  • Findings may include inferred OS or service versions

  • False positives may occur due to banner analysis

These scans should not be used as a replacement for internal authenticated scanning.

Performance Considerations

Scan duration and results are influenced by:

  • Number of IP addresses in scope

  • Network latency and routing

  • Firewall filtering or rate-limiting behavior

External IP scans are typically fast and lightweight.

Common Limitations

  • Only internet-facing services are assessed

  • Internal-only systems are not visible

  • Network filtering may obscure some services

  • Results reflect exposure at the time of scanning

Best Practices

  • Ensure Cyrisma scanning IPs are allowlisted in perimeter firewalls

  • Run external IP scans regularly to monitor perimeter exposure

  • Investigate unexpected open ports or services immediately

  • Correlate findings with firewall and network configurations

  • Use external scans as an early warning system, not a sole control