Answer: Port 37 is primarily associated with the TIME protocol, a legacy service for time synchronization. It transmits Coordinated Universal Time (UTC) in seconds since January 1, 1900. While largely replaced by NTP (Port 123), some industrial systems and legacy infrastructure still use Port 37 for basic timekeeping. Modern operating systems rarely enable it by default due to security risks.
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What Is the TIME Protocol and How Does It Use Port 37?
The TIME protocol, standardized in RFC 868, operates on Port 37 using both TCP and UDP. It provides a 32-bit binary number representing UTC time, excluding timezone or daylight saving adjustments. Unlike NTP, it lacks error correction or encryption, making it obsolete for precision-critical applications but historically significant in early network time synchronization.
Why Has Port 37 Become Obsolete in Modern Networks?
Port 37’s decline stems from three factors: 1) Limited precision (±2 seconds vs NTP’s milliseconds), 2) No security features against spoofing attacks, and 3) Incompatibility with IPv6 addressing. The Internet Engineering Task Force (IETF) deprecated it in 2016, recommending NTP or SNTP for all new implementations requiring network time synchronization.
The protocol’s 32-bit timestamp format also introduces a looming technical debt known as the “Year 2038 Problem,” where systems using TIME protocol will overflow their time counters on February 7, 2036. This issue predates the more widely discussed Unix 2038 problem by two years. Modern cybersecurity frameworks like NIST SP 800-82 Rev. 3 explicitly flag Port 37 as a potential attack vector due to its lack of authentication mechanisms. In 2022, researchers demonstrated how attackers could manipulate Port 37 timestamps to bypass industrial control system safety interlocks, highlighting why migration to NTP is critical for operational technology environments.
How Does Port 37 Compare to Modern Time Synchronization Methods?
| Feature | Port 37 (TIME) | Port 123 (NTP) |
| Precision | ±2 seconds | ±10 milliseconds |
| Security | None | Autokey, NTS |
| IPv6 Support | No | Yes |
| Leap Second Handling | Manual | Automatic |
What Are the Security Implications of Using Port 37?
Open Port 37 exposes systems to: 1) Time spoofing attacks disrupting scheduled operations, 2) Amplification DDoS vulnerabilities (6:1 attack ratio), and 3) Fingerprinting of legacy systems. The 2021 CISA advisory (AA21-131A) specifically lists Port 37 among services to disable in critical infrastructure unless required for backwards compatibility.
Where Is Port 37 Still Actively Used Today?
Niche applications include: 1) Aviation ACARS systems, 2) SCADA controllers in oil/gas pipelines, 3) Retrocomputing environments. A 2023 Shodan scan shows 1,412 exposed Port 37 devices, predominantly in manufacturing (34%), utilities (28%), and academic legacy systems (19%).
In maritime navigation systems, Port 37 remains embedded in older AIS (Automatic Identification System) implementations due to certification requirements that predate modern NTP adoption. The U.S. Federal Aviation Administration’s Technical Center reports approximately 87 active Port 37 nodes in legacy radar timing systems scheduled for replacement by 2027. Museums preserving early internet infrastructure, like the Computer History Museum’s 1970s-era PDP-11 installation, maintain Port 37 services for historical accuracy during demonstrations of ARPANET-era networking protocols.
How Can Organizations Detect and Secure Port 37 Services?
Three-step mitigation: 1) Network scanning with Nmap (nmap -p 37 --script time-protocol), 2) Disable Windows TIME via Group Policy (Computer Configuration → Administrative Templates → System → Windows Time Service), 3) Implement firewall rules blocking Port 37 ingress/egress except for verified legacy systems requiring TIME protocol functionality.
“Port 37 represents a fascinating case study in protocol evolution. While its 32-bit time format seemed sufficient in 1983, the Y2.038k problem (when its counter overflows) will make remaining systems vulnerable decades before the Unix 2038 crisis. Organizations clinging to TIME protocol must implement gateway translators to NTP immediately.”
— Network Time Foundation Architect
Conclusion
Port 37’s role has transitioned from essential internet infrastructure to a historical curiosity. While understanding its function remains crucial for legacy system maintenance, modern networks should prioritize NTPv4 or PTP (IEEE 1588) for time-sensitive operations. Regular port audits and protocol updates are critical in mitigating risks associated with obsolete services like TIME protocol.
FAQs
- Q: Why don’t modern OSs use Port 37 by default?
- A: Security concerns and precision limitations led Microsoft, Linux distributions, and BSD variants to disable TIME protocol services post-2008. Windows Server 2008 R2 was the last version with enabled-by-default Port 37 support.
- Q: Can Port 37 and NTP coexist?
- A: Yes, but require separate stratum configurations. However, RFC 863 explicitly advises against parallel operation due to potential time source conflicts and increased attack surface.
- Q: How to test Port 37 functionality?
- A: Use
netcatcommand:nc -u [host] 37 | hexdump(UDP) ortelnet [host] 37(TCP). Valid response contains 4 bytes representing seconds since 1900 epoch.