+NAME="AEN878"
+>4.12. Can Privoxy act as a <SPAN
+CLASS="QUOTE"
+>"caching"</SPAN
+> proxy to
+speed up web browsing?</A
+></H3
+><P
+> No, it does not have this ability at all. You want something like
+ <A
+HREF="http://www.squid-cache.org/"
+TARGET="_top"
+>Squid</A
+> or
+ <A
+HREF="http://www.pps.jussieu.fr/~jch/software/polipo/"
+TARGET="_top"
+>Polipo</A
+> for this.
+ And, yes, before you ask, <SPAN
+CLASS="APPLICATION"
+>Privoxy</SPAN
+> can co-exist
+ with other kinds of proxies like <SPAN
+CLASS="APPLICATION"
+>Squid</SPAN
+>.
+ See the <A
+HREF="../user-manual/config.html#FORWARDING"
+TARGET="_top"
+>forwarding
+ chapter</A
+> in the <A
+HREF="../user-manual/index.html"
+TARGET="_top"
+>user
+ manual</A
+> for details.</P
+></DIV
+><DIV
+CLASS="SECT2"
+><H3
+CLASS="SECT2"
+><A
+NAME="AEN888"
+>4.13. What about as a firewall? Can Privoxy protect me?</A
+></H3
+><P
+> Not in the way you mean, or in the way some firewall vendors claim they can.
+ <SPAN
+CLASS="APPLICATION"
+>Privoxy</SPAN
+> can help protect your privacy, but can't
+ protect your system from intrusion attempts. It is, of course, perfectly possible
+ to use <SPAN
+CLASS="emphasis"
+><I
+CLASS="EMPHASIS"
+>both</I
+></SPAN
+>.</P
+></DIV
+><DIV
+CLASS="SECT2"
+><H3
+CLASS="SECT2"
+><A
+NAME="AEN893"
+>4.14. I have large empty spaces / a checkerboard pattern now where
+ads used to be. Why?</A
+></H3
+><P
+> It is technically possible to eliminate banners and ads in a way that frees
+ their allocated page space. This could easily be done by blocking with
+ <SPAN
+CLASS="APPLICATION"
+>Privoxy's</SPAN
+> filters,
+ and eliminating the <SPAN
+CLASS="emphasis"
+><I
+CLASS="EMPHASIS"
+>entire</I
+></SPAN
+> image references from the
+ HTML page source. </P
+><P
+> But, this would consume considerably more CPU resources (IOW, slow things
+ down), would likely destroy the layout of some web pages which rely on the
+ banners utilizing a certain amount of page space, and might fail in other
+ cases, where the screen space is reserved (e.g. by HTML tables for instance).
+ Also, making ads and banners disappear without any trace complicates
+ troubleshooting, and would sooner or later be problematic.</P
+><P
+> The better alternative is to instead let them stay, and block the resulting
+ requests for the banners themselves as is now the case. This leaves either
+ empty space, or the familiar checkerboard pattern.</P
+><P
+> So the developers won't support this in the default configuration, but you
+ can of course define appropriate filters yourself to achieve this.</P
+></DIV
+><DIV
+CLASS="SECT2"
+><H3
+CLASS="SECT2"
+><A
+NAME="AEN901"
+>4.15. How can Privoxy filter Secure (HTTPS) URLs?</A
+></H3
+><P
+> Since secure HTTP connections are encrypted SSL sessions between your browser
+ and the secure site, and are meant to be reliably <SPAN
+CLASS="emphasis"
+><I
+CLASS="EMPHASIS"
+>secure</I
+></SPAN
+>,
+ there is little that <SPAN
+CLASS="APPLICATION"
+>Privoxy</SPAN
+> can do but hand the raw
+ gibberish data though from one end to the other unprocessed.</P
+><P
+> The only exception to this is blocking by host patterns, as the client needs
+ to tell <SPAN
+CLASS="APPLICATION"
+>Privoxy</SPAN
+> the name of the remote server,
+ so that <SPAN
+CLASS="APPLICATION"
+>Privoxy</SPAN
+> can establish the connection.
+ If that name matches a host-only pattern, the connection will be blocked.</P
+><P
+> As far as ad blocking is concerned, this is less of a restriction than it may
+ seem, since ad sources are often identifiable by the host name, and often
+ the banners to be placed in an encrypted page come unencrypted nonetheless
+ for efficiency reasons, which exposes them to the full power of
+ <SPAN
+CLASS="APPLICATION"
+>Privoxy</SPAN
+>'s ad blocking.</P
+><P
+> <SPAN
+CLASS="QUOTE"
+>"Content cookies"</SPAN
+> (those that are embedded in the actual HTML or
+ JS page content, see <TT
+CLASS="LITERAL"
+><A
+HREF="../user-manual/actions-file.html#FILTER-CONTENT-COOKIES"
+TARGET="_top"
+>filter{content-cookies}</A
+></TT
+>),
+ in an SSL transaction will be impossible to block under these conditions.
+ Fortunately, this does not seem to be a very common scenario since most
+ cookies come by traditional means.</P
+></DIV
+><DIV
+CLASS="SECT2"
+><H3
+CLASS="SECT2"
+><A
+NAME="AEN915"
+>4.16. Privoxy runs as a <SPAN
+CLASS="QUOTE"
+>"server"</SPAN
+>. How
+secure is it? Do I need to take any special precautions?</A
+></H3
+><P
+> On Unix-like systems, <SPAN
+CLASS="APPLICATION"
+>Privoxy</SPAN
+> can run as a non-privileged
+ user, which is how we recommend it be run. Also, by default
+ <SPAN
+CLASS="APPLICATION"
+>Privoxy</SPAN
+> listens to requests from <SPAN
+CLASS="QUOTE"
+>"localhost"</SPAN
+>
+ only.</P
+><P
+> The server aspect of <SPAN
+CLASS="APPLICATION"
+>Privoxy</SPAN
+> is not itself directly
+ exposed to the Internet in this configuration. If you want to have
+ <SPAN
+CLASS="APPLICATION"
+>Privoxy</SPAN
+> serve as a LAN proxy, this will have to
+ be opened up to allow for LAN requests. In this case, we'd recommend
+ you specify only the LAN gateway address, e.g. 192.168.1.1, in the main
+ <SPAN