Port 5667NSCA
NSCA (Nagios Service Check Acceptor) is a utility used to securely send passive check results from remote systems and client hosts to a central Nagios monitoring server. It facilitates distributed monitoring by allowing multiple external systems to report their status centrally, improving scalability and extending Nagios capabilities..
- transport
- tcp
- in transit
- cleartext
- assignment
- unofficial
- risk
- 4/10
- lookups
- 8,551
single transport
payload readable on path
used by convention
caution
rank 588 of 993 · top 59%
Technical Details
what runs on :5667NSCA, or Nagios Service Check Acceptor, is an add-on component designed for the Nagios monitoring framework. It enables distributed monitoring by allowing client systems to send passive check results asynchronously to the central server. Passive checks are generated externally by applications or scripts and transmitted via NSCA to update Nagios on the health status of various hosts and services.
The NSCA daemon listens on port 5667 for incoming messages sent by the nsca_send client utility running on remote hosts. The communication protocol involves a well-defined binary format that contains the host or service information, return code, and status output. While NSCA initially supported plaintext transmission, it has options for encryption to protect sensitive monitoring data during transit. However, this encryption is often considered weak compared to modern standards.
In typical deployments, NSCA is favored for environments with distributed systems or where active polling is impractical due to firewall restrictions or scalability concerns. It complements Nagios by reducing load on the central server and enabling timely updates in complex or segmented network topologies.
Security Information
exposure of :5667risk 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
unofficial
used by convention, not registered — what answers here varies by deployment
reachable over
tcp
every listening transport is another surface to filter at the edge
security overview
Common vulnerabilities of NSCA include:
- Weak cipher support and outdated encryption methods, which can expose sensitive monitoring data if intercepted.
- Lack of strong authentication, making it susceptible to spoofed passive check submissions by attackers.
- Potential for Denial-of-Service (DoS) by flooding the NSCA daemon with excessive or malformed data.
Common mitigations involve:
- Using secure network channels like VPNs or SSH tunnels to encapsulate NSCA traffic.
- Restricting source IPs via firewall rules or tcpwrappers to allow only trusted hosts.
- Transitioning to more secure mechanisms such as NSClient++ over encrypted channels, NRDP (which uses HTTPS), or other modern agents.
- Staying updated with Nagios-related plugins and disabling weakly encrypted modes if possible.
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risk mix of the 8 listed
- caution100%
0 of 8 encrypted