---
title: "NET-FW-001 No Active Host Firewall"
canonical: https://openvapt.com/checks/NET-FW-001.html
html: https://openvapt.com/checks/NET-FW-001.html
site: OpenVAPT, https://openvapt.com/
license: OpenVAPT Source-Available Licence 1.3, https://openvapt.com/legal/licence-text.html
modified: 2026-10-14
version: 0.1.0-alpha.6
---

# NET-FW-001 No Active Host Firewall

Checks whether a host firewall (nftables, iptables, ufw or firewalld) is filtering incoming traffic.

- Domain: Network
- Severity: Medium
- Control category: Network Exposure
- Fix effort: medium
- CVSS v3.1 vector: `CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:L`
- CIS Controls v8: 4.4
- NIST CSF 2.0: PR.IR-01
- CWE: CWE-923
- NIST SP 800-53 Rev. 5: SC-7
- Benchmark topic: Host-based firewall configured (topic only, no benchmark text)

## Why It Matters

A default-deny host firewall is a safety net: a service that is installed or misconfigured by mistake is still not reachable from the internet.

## How It Detects

Runs read-only status commands in order: ufw status, firewall-cmd --state, nft list ruleset, iptables -S. Passes if ufw/firewalld report active, or if nftables/iptables contain a drop/reject rule or a DROP input policy.

## How to Fix

Ubuntu: ufw default deny incoming && ufw allow OpenSSH && ufw allow 80,443/tcp && ufw enable . RHEL family: systemctl enable --now firewalld . Always allow SSH before enabling, or you will lock yourself out.

## How to Verify

```
ufw status verbose  or  firewall-cmd --list-all  or  nft list ruleset
```

## Learn the Theory

- [F1 Security Basics](https://openvapt.com/academy/f1.md)
- [P3 Network Exposure and Firewalls](https://openvapt.com/academy/p3.md)

## References

- [NIST SP 800-41 Rev. 1, Guidelines on Firewalls and Firewall Policy](https://csrc.nist.gov/pubs/sp/800/41/r1/final)
- [nftables wiki](https://wiki.nftables.org/wiki-nftables/index.php/Main_Page)

## Source Code

https://github.com/OpenVAPT/openvapt/blob/574f7f3333c44b75a3c649e2d93a76d507f75adf/internal/checks/network/firewall.go

Run it: `openvapt scan --only NET-FW-001`. Read it offline: `openvapt explain NET-FW-001`.

---

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