---
title: "NET-SVC-001 Cleartext Legacy Services Listening"
canonical: https://openvapt.com/checks/NET-SVC-001.html
html: https://openvapt.com/checks/NET-SVC-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-SVC-001 Cleartext Legacy Services Listening

Checks for Telnet, FTP, rsh/rlogin, TFTP, plain POP3/IMAP/LDAP, SNMP v1/v2c and rsync daemons on network-reachable addresses.

- Domain: Network
- Severity: High
- 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:H/I:H/A:N`
- CIS Controls v8: 4.8
- NIST CSF 2.0: PR.PS-01, PR.IR-01
- CWE: CWE-319
- OWASP Top 10 2021: A02:2021
- NIST SP 800-53 Rev. 5: SC-8, CM-7
- Benchmark topic: Remove insecure legacy services (topic only, no benchmark text)

## Why It Matters

These protocols send passwords and data unencrypted, so anyone on the path can read or alter them. Most also have weak or no authentication.

## How It Detects

Matches network-reachable listening ports from /proc/net against well-known cleartext service ports.

## How to Fix

Replace with encrypted equivalents: SSH/SFTP instead of Telnet/FTP/rsh, IMAPS (993)/POP3S (995), LDAPS (636), SNMPv3. Disable the old service: systemctl disable --now <unit>.

## How to Verify

```
ss -tulpn  should not show ports 21, 23, 69, 110, 143, 161, 389, 512-514 or 873 on public addresses.
```

## Learn the Theory

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

## References

- [NIST SP 800-123, Guide to General Server Security](https://csrc.nist.gov/pubs/sp/800/123/final)

## Source Code

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

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

---

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