---
title: "NET-LSN-001 Inventory of Listening Network Services"
canonical: https://openvapt.com/checks/NET-LSN-001.html
html: https://openvapt.com/checks/NET-LSN-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-LSN-001 Inventory of Listening Network Services

Lists every TCP and UDP port this machine listens on, and whether it is reachable from other machines.

- Domain: Network
- Severity: Info
- Control category: Network Exposure
- Fix effort: low
- CVSS v3.1 vector: `CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:N`
- CIS Controls v8: 4.8
- NIST CSF 2.0: PR.PS-01, PR.IR-01
- CWE: CWE-1327
- NIST SP 800-53 Rev. 5: CM-7, CM-8
- Benchmark topic: Network services inventory (topic only, no benchmark text)

## Why It Matters

Attack surface starts with what is listening. Every exposed port should be known and justified (NIST SP 800-115, discovery phase).

## How It Detects

Parses /proc/net/tcp, tcp6, udp and udp6. Sockets bound to 127.0.0.1 or ::1 are local only; anything else (0.0.0.0, ::, a public address) is reachable from the network unless a firewall blocks it.

## How to Fix

Stop or uninstall services you do not need (systemctl disable --now <unit>). Bind internal services to 127.0.0.1. Block the rest at the firewall.

## How to Verify

```
ss -tulpn  shows the same list with process names.
```

## Learn the Theory

- [F2 What VAPT Is, and Doing It Legally](https://openvapt.com/academy/f2.md)
- [P3 Network Exposure and Firewalls](https://openvapt.com/academy/p3.md)
- [A1 Running an Assessment](https://openvapt.com/academy/a1.md)

## References

- [NIST SP 800-115, Technical Guide to Information Security Testing and Assessment](https://csrc.nist.gov/pubs/sp/800/115/final)
- [proc_net(5), Linux man-pages](https://man7.org/linux/man-pages/man5/proc_net.5.html)

## Source Code

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

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

---

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