whatportis.com
suggest an edit →

Port 991Netnews Administration System

**NAS (Netnews Administration System)** is a protocol designed to manage and facilitate the administration of Usenet newsgroups, allowing for efficient control of news server configurations, moderation settings, and distribution policies. Operating over both TCP and UDP, it assists administrators in maintaining the integrity and smooth operation of news distribution networks..

inNetwork ServicesSystem
transport
tcp · udp

2 transports registered

in transit
cleartext

payload readable on path

assignment
official

registered with iana

risk
4/10

caution

lookups
17,907

rank 153 of 993 · top 15%

Technical Details

what runs on :991

Overview:

The Netnews Administration System (NAS) operates primarily as a control and management protocol for Usenet news servers and distribution systems. Running typically on port 991 over both TCP and UDP, it facilitates administrative tasks such as managing feed configurations, enforcing moderation controls, and synchronizing operational policies among distributed news servers.

Functionality:

NAS streamlines complex moderation workflows by allowing configuration commands and status updates to be transmitted between network nodes. It supports administrative commands, status queries, and automated control messages, ensuring that newsgroups operate according to established guidelines. The protocol may interoperate with NNTP (Network News Transfer Protocol) to assist in overall newsgroup data management albeit focusing more on the administrative aspects.

Architecture:

Designed with flexibility, NAS can perform both synchronous and asynchronous communications. The use of TCP ensures reliable command delivery, while UDP supports faster, low-overhead status broadcasts when reliability can be sacrificed for performance. Although it is an official port assignment, NAS adoption is somewhat limited today due to the decline of Usenet usage and preference for web-based forums.

Security Information

exposure of :991

risk score

4/ 10caution

worth attention. how exposed you are depends on configuration — don't leave it reachable from the internet without a reason.

network services averages 3.9 across 604 ports — this one sits 0.1 above.

in transit

cleartext

credentials and payloads are readable by anyone on path

assignment

official

registered with iana for this service — scanners fingerprint it by number

reachable over

tcp · udp

udp is connectionless — source addresses are trivially spoofed and it is a reflection favourite

security overview

Common Vulnerabilities:

  • Lack of encryption makes NAS susceptible to eavesdropping, enabling attackers to intercept sensitive administrative commands or user data.
  • If improperly configured, unauthorized access could allow malicious entities to alter moderation settings or disrupt distribution channels.
  • Spoofed UDP messages can be exploited for Denial-of-Service (DoS) attacks by overwhelming servers or causing configuration inconsistencies.

Common Mitigations:

  • Restrict access to trusted administrative hosts via network firewalls and access control lists.
  • Tunneling NAS traffic over secure channels like VPNs or SSH to compensate for lack of native encryption.
  • Implement strong authentication and role-based access controls to prevent unauthorized configuration changes.
  • Regularly monitor network traffic and audit logs to detect misuse or intrusion attempts.
  • Disable unused protocols (e.g., UDP) or ports if not required, further reducing the attack surface.

Related Ports

all 604 in network services →

the 8 most looked-up other ports in network services — 604 ports carry that label.

portservicerisk
:9080Groove RPCcaution
:6543Jetnetcaution
:5938TeamViewercaution
:8291Winbox MikroTik Admincaution
:3233WhiskerControl Protocolcaution
:3268Microsoft Global Catalog (GC)caution
:135Microsoft EPMAPcaution
:3128Tatsoft Default HTTP Proxycaution

risk mix of the 8 listed

  • caution100%

0 of 8 encrypted