I asked this question at stackoverflow but I didn't recvie any solutions so I think the good people at serverfault may be able to help.
All the resources I've read explains how to prevent access to an entire directory based on IP but doesn't explain how to do this for a single file.
This is what is used to protect a directory:
<Limit GET POST PUT> order deny,allow deny from all allow from 123.456.78.910 </Limit>
^ here only the IP 123.456.78.910 will have access to the directory in which that rule is placed. But the question again is, How to do this for a single file?