The easiest "built in" method is to use the DataSocket Read VI, which can grab an arbitrary file via HTTP or FTP as long as you append the string "[text]" to the end of the URL. See the
Retrieving an Unformatted Text File via FTP or HTTP Using DataSocket KnowledgeBase entry.
In your case, use the following input for the "connection in" input:
http://sine.ni.com/images/global/us/logo.gif[text]
If you wire a string to the "type (Variant)" input, the output can be written directly to a file.
Regards,
John