Port 543klogin (Kerberos Login)
Kerberos klogin facilitates secure, authenticated remote login services using Kerberos as the authentication mechanism. It is a protocol built on top of the Berkeley rlogin protocol but with strong authentication to prevent credential interception or replay attacks. Historically, it served to allow trusted access between hosts in environments where Kerberos is deployed..
- transport
- tcp
- in transit
- cleartext
- assignment
- official
- risk
- 2/10
- lookups
- 11,312
single transport
payload readable on path
registered with iana
safe
rank 368 of 993 · top 37%
Technical Details
what runs on :543klogin is a Kerberos-enhanced remote login protocol that extends the traditional Unix rlogin service. Unlike the original rlogin, which transmits credentials in plaintext, klogin leverages Kerberos tickets to authenticate users securely. It typically operates over TCP on port 543 as a dedicated channel for these secure login sessions.
In the Kerberos authentication process, the client first obtains a service ticket from the Kerberos Key Distribution Center (KDC). This ticket is then presented to the server during connection initiation, allowing mutual authentication without transmitting reusable credentials across the network. This process mitigates risks associated with network eavesdropping.
Given its foundation on legacy protocols, klogin was designed to integrate with existing rlogin infrastructures, simplifying secure transition for organizations adopting Kerberos. However, as SSH gained popularity with integrated encryption and easier deployment, klogin usage has significantly declined but may still be encountered in legacy Kerberos-secured environments.
Security Information
exposure of :543risk score
2/ 10safe
routine exposure. this port is rarely the way in on its own — keep it patched and logged and move on.
security averages 3.8 across 216 ports — this one sits 1.8 below.
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:
- Absence of data encryption, exposing session data to potential sniffing.
- Susceptibility to replay attacks if Kerberos tickets are compromised.
- Weaknesses inherent in legacy rlogin protocol, such as trust-based authentication models and potential buffer overflows.
Common Mitigations:
- Enforce strict ticket expiry and renewable policies to reduce ticket misuse.
- Utilize strong Kerberos policies, including pre-authentication and multi-factor integration.
- Restrict klogin access via network segmentation and firewall rules.
- Where possible, migrate to encrypted alternatives like SSH, which provide stronger confidentiality and integrity guarantees.
- Regularly audit Kerberos ticket usage and monitor for anomalous access patterns.
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risk mix of the 8 listed
- caution100%
3 of 8 encrypted