Port 517Talk Daemon
Port 517 is assigned for the Talk service, an early Unix-based text communication protocol. It enabled real-time messaging between users on different systems using a split-screen interface, facilitating interactive conversations before the advent of modern instant messaging platforms..
- transport
- udp
- in transit
- cleartext
- assignment
- official
- risk
- 4/10
- lookups
- 5,029
single transport
payload readable on path
registered with iana
caution
rank 918 of 993 · top 92%
Technical Details
what runs on :517The Talk protocol, traditionally operating over UDP port 517, was developed to allow two users on Unix systems to engage in real-time, interactive text conversations. The service employs a split-screen interface where each participant can simultaneously compose and view messages. Communication occurs by broadcasting requests and responses across the network, coordinating session initiation between client and server.
Behind the scenes, a client sends invitation packets over UDP port 517 to locate the intended recipient's talk daemon. The server daemon then mediates the connection establishment, negotiating which host acts as the listener. Once the connection is accepted, the actual chat data is transmitted over a separate negotiated channel, usually TCP port 518 or a dynamically assigned port, to allow continuous, bidirectional communication.
Due to its simplicity, the Talk protocol lacks advanced features or encryption. Its reliance on broadcast messages and unprotected traffic limits its scalability and security, which contributed to its gradual obsolescence with the emergence of more sophisticated chat systems.
Security Information
exposure of :517risk 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
udp
udp is connectionless — source addresses are trivially spoofed and it is a reflection favourite
security overview
Common Vulnerabilities:
- Susceptible to spoofing and man-in-the-middle attacks due to the lack of authentication mechanisms.
- Exposed to denial of service (DoS) attacks by sending crafted invitation packets to overwhelm the daemon.
- Vulnerable to eavesdropping since messages are transmitted in plaintext without encryption.
- May serve as an entry point for exploitation if legacy daemons have unpatched vulnerabilities.
Common Mitigations:
- Disable or block UDP port 517 on network firewalls unless the service is explicitly required.
- Replace legacy Talk implementations with more secure messaging solutions supporting encryption and authentication.
- Employ network intrusion detection systems (IDS) to monitor for suspicious activity targeting this port.
- Restrict Talk service usage to trusted, segmented networks to limit potential attack vectors.
Related Ports
the 8 most looked-up other ports in network services — 604 ports carry that label.
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|---|---|---|---|---|---|
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| :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