Port 23399Skype Protocol
Skype primarily uses port 23399 for its peer-to-peer communications, enabling voice, video, and instant messaging. This port facilitates the connection through Skype's custom protocol, allowing users worldwide to communicate seamlessly across various network configurations..
- transport
- unknown
- in transit
- cleartext
- assignment
- unofficial
- risk
- 4/10
- lookups
- 8,797
single transport
payload readable on path
used by convention
caution
rank 569 of 993 · top 57%
Technical Details
what runs on :23399Skype utilizes proprietary protocols to establish direct or relay communications between clients. Port 23399 is commonly associated with Skype’s Default Protocol, which aids in peer discovery and connection establishment when other preferred ports are unavailable. It assists Skype in negotiating NAT traversal and firewall bypassing mechanisms.
Skype’s protocol adapts dynamically depending on the network environment, choosing between UDP and TCP variants or custom implementations. It uses port 23399 primarily as a fallback, helping maintain service connectivity and reliability across restrictive or variable network conditions.
Moreover, this port manages signalling, call setup, and media relay aspects essential to the Skype architecture. Since the protocol is proprietary, specific details on message formatting and encryption remain undisclosed, though it heavily relies on Microsoft’s cloud infrastructure for control and authentication services.
Security Information
exposure of :23399risk score
4/ 10caution
worth attention. how exposed you are depends on configuration — don't leave it reachable from the internet without a reason.
voice and chat averages 3.9 across 120 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
unknown
every listening transport is another surface to filter at the edge
security overview
Common Vulnerabilities:
- Potential for abuse due to proprietary, undocumented protocol, making security auditing difficult
- Possibility of exploitation through malformed payload delivery or protocol fuzzing
- Use in undesired data exfiltration or covert communication channels
- Susceptibility to man-in-the-middle attacks if communications are not properly encrypted
Common Mitigations:
- Enforce strict firewall blocking when Skype traffic is unauthorized
- Monitor network traffic patterns to detect anomalous or unauthorized usage
- Restrict unmanaged Skype client software within sensitive environments
- Keep Skype applications and associated services updated to patch known vulnerabilities
- Utilize network segmentation and Zero Trust principles to minimize lateral movement risk
- Log and audit VoIP and messaging traffic regularly
Related Ports
the 8 most looked-up other ports in voice and chat — 120 ports carry that label.
| port | service | risk | |||
|---|---|---|---|---|---|
| :9090 | Openfire Admin Console | TCP | Web Services | caution | 34.2k |
| :1513 | Garena Gaming | TCPUDP | Gaming | caution | 33.1k |
| :9091 | Openfire Admin Console (SSL) | TCPtls | Web Services | caution | 28.3k |
| :2031 | Mobrien Chat | TCPUDP | Web Services | caution | 27.7k |
| :1720 | H.323 Signaling | TCP | Network Services | caution | 26.5k |
| :6005 | Camfrog Chat | TCP | Voice and Chat | caution | 25.2k |
| :3001 | Miralix Phone Monitor | TCP | Network Services | caution | 21.7k |
| :9009 | Pichat Server | TCPUDP | Network Services | caution | 19.7k |
risk mix of the 8 listed
- caution100%
1 of 8 encrypted