The Windows 2000 telnet client attempts to perform NTLM authentication by default, which allows remote attackers to capture and replay the NTLM challenge/response via a telnet:// URL that points to the malicious server, aka the "Windows 2000 Telnet Client NTLM Authentication" vulnerability.
https://exchange.xforce.ibmcloud.com/vulnerabilities/5242
https://docs.microsoft.com/en-us/security-updates/securitybulletins/2000/ms00-067
http://www.atstake.com/research/advisories/2000/a091400-1.txt