Port 101NIC Hostname Service
Port 101, commonly known as the NIC Hostname Service, was historically used to provide host name information over TCP/IP networks. Though largely obsolete today, it played a role in early networked host identification before the widespread adoption of DNS..
- transport
- tcp
- in transit
- cleartext
- assignment
- official
- risk
- 4/10
- lookups
- 5,704
single transport
payload readable on path
registered with iana
caution
rank 860 of 993 · top 87%
Technical Details
what runs on :101Overview:
Port 101 TCP historically served a service provided by the Network Information Center (NIC) that enabled retrieving a system's hostname. This was an early method for obtaining machine identification information across the ARPANET and early internet.
Protocol Details:
The NIC Hostname Service allowed devices or users to connect via a simple TCP socket to query textual hostname information from a remote computer or server. The protocol was straightforward, primarily handling clear text hostname responses without complex negotiation or authentication mechanisms. Operations generally entailed a connection request, submission of a query, then receiving a human-readable output.
Modern Context:
This port and associated service have largely fallen out of use with the development of more robust and scalable naming systems like DNS (Domain Name System). Modern networks rarely expose this service, and port 101 is mostly seen in historical documentation or legacy network environments. Legacy devices or highly bespoke systems may theoretically still use this, but its operational presence is negligible today.
Security Information
exposure of :101risk 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
every listening transport is another surface to filter at the edge
security overview
Common Vulnerabilities:
- As the service lacks authentication, it was vulnerable to information leakage if exposed publicly.
- Cleartext responses make it susceptible to eavesdropping or interception.
- Could be exploited in reconnaissance phases by attackers mapping network assets.
Common Mitigations:
- Disable the service if not explicitly required.
- Filter port 101 traffic at firewall and perimeter devices to prevent unwanted access.
- Use encrypted or authenticated naming protocols (e.g., DNSSEC) in production environments.
- Conduct regular scans to ensure port 101 is not inadvertently exposed externally.
- Monitor logs for unexpected connection attempts to this port as part of network anomaly detection.
Related Ports
the 8 most looked-up other ports in network services — 604 ports carry that label.
| port | service | risk | |||
|---|---|---|---|---|---|
| :9080 | Groove RPC | TCPUDP | Web Services | caution | 70.8k |
| :6543 | Jetnet | UDP | Network Services | caution | 65.3k |
| :5938 | TeamViewer | TCPUDP | Remote Access | caution | 65.0k |
| :8291 | Winbox MikroTik Admin | TCP | Security | caution | 62.9k |
| :3233 | WhiskerControl Protocol | TCPUDP | Network Services | caution | 61.9k |
| :3268 | Microsoft Global Catalog (GC) | TCPUDP | Security | caution | 54.6k |
| :135 | Microsoft EPMAP | TCPUDP | Security | caution | 51.9k |
| :3128 | Tatsoft Default HTTP Proxy | TCP | Web Services | caution | 46.8k |
risk mix of the 8 listed
- caution100%
0 of 8 encrypted