I recently went to http://whatismyipaddress.com and

And under the front page under “Proxy Server Detected!” I saw the internal hostname of my squid proxy.

Which may or may not be a security problem (giving away an internal domain name and hostname).

So inside squid.conf I set

# add this to /etc/squid/squid.conf
visible_hostname mybogusproxyhostname.local
# and while we are at it stop squid blabbing about it's version aswell
httpd_suppress_version_string on

# then restart squid
/etc/init.d/squid restart

Now my proxy hostname is reported as the visible_hostname setting.