---
title: "NET-SVC-003 Network Time Service Amplification Risk"
canonical: https://openvapt.com/checks/NET-SVC-003.html
html: https://openvapt.com/checks/NET-SVC-003.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-SVC-003 Network Time Service Amplification Risk

NTP or chrony serves broad clients or permits legacy monitoring commands that can amplify traffic.

- Domain: Network
- Severity: High
- 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:H`
- CIS Controls v8: 4.8
- NIST CSF 2.0: PR.PS-01, PR.IR-01
- CWE: CWE-406
- NIST SP 800-53 Rev. 5: SC-5, SC-7

## Why It Matters

Internet-reachable time services with broad client access or legacy mode 6 or 7 controls can be abused for reflection and amplification.

## How It Detects

When UDP port 123 is network-reachable, reads ntp.conf or chrony.conf and flags broad allow directives or missing noquery restrictions.

## How to Fix

Bind the time daemon to required interfaces, restrict clients to explicit networks, disable monitoring, and use noquery or equivalent controls.

## How to Verify

```
Confirm UDP port 123 is filtered from untrusted networks and review the daemon's effective access restrictions.
```

## Learn the Theory

- [P3 Network Exposure and Firewalls](https://openvapt.com/academy/p3.md)
- [P8 Data Services: Databases, File Shares, DNS and Mail](https://openvapt.com/academy/p8.md)

## References

- [CISA Alert TA14-013A, NTP Amplification Attacks Using CVE-2013-5211](https://www.cisa.gov/news-events/alerts/2014/01/13/ntp-amplification-attacks-using-cve-2013-5211)
- [chrony Documentation - Access Control](https://chrony-project.org/doc/4.6/chrony.conf.html)

## Source Code

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

Run it: `openvapt scan --only NET-SVC-003`. Read it offline: `openvapt explain NET-SVC-003`.

---

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