ftp.us.debian.org

$ host ftp.us.debian.org.
ftp.us.debian.org has address 128.30.2.36
ftp.us.debian.org has address 64.50.238.52
ftp.us.debian.org has address 64.50.236.52
ftp.us.debian.org has address 35.9.37.225

$ telnet ftp.us.debian.org 80
Trying 35.9.37.225...
Connected to ftp.us.debian.org.
Escape character is '^]'.
HEAD / HTTP/1.0

HTTP/1.0 200 OK
Connection: close
Content-Type: text/html
Content-Length: 2949
Date: Tue, 03 Jun 2008 22:36:34 GMT
Server: Microsoft-IIS/6.0

Connection closed by foreign host.

Excuse me?

$ whois 35.9.37.225
Merit Network Inc. MICH-1 (NET-35-0-0-0-1) 
                                  35.0.0.0 - 35.255.255.255
Michigan State University MICH-618 (NET-35-8-0-0-1) 
                                  35.8.0.0 - 35.10.255.255

# ARIN WHOIS database, last updated 2008-06-02 19:10
# Enter ? for additional hints on searching ARIN's WHOIS database.

Why, exactly, is Michigan State running an official Debian mirror on IIS?

The three other hosts run a real OS/webserver.