[tor-talk] An external application is needed...

Joe Btfsplk joebtfsplk at gmx.com
Fri Mar 9 17:41:58 UTC 2012

On 3/9/2012 9:17 AM, Tor User0000 wrote:
> Hi,
> I was always wondering why I get the following pop-up message when
> downloading a file. And it does not happen all the time. Why it says that
> an external app is needed when only opening the download window?
> *An external application is needed to handle:
> https://www.torproject.org/dist/torbrowser/linux/tor-browser-gnu-linux-i686-2.2.35-7.2-dev-en-US.tar.gz
> NOTE: External applications are NOT Tor safe by default and can unmask you!
> If this file is untrusted, you should either save it to view while offline
> or in a VM,
> or consider using a transparent Tor proxy like Tails LiveCD or torsocks.
> *Thanks for the help! :-)*
The difference, I believe, is when there is an option of either opening 
the file w/ some application(s) or d/l it, Tor browser / Torbutton warns 
that not all applications will preserve anonymity, if launched inside 
Tor / TBB.  Whether you get the pop up could depend on how you have set 
the browser (& perhaps certain applications) to handle diff file types.

Like in Firefox, under Options>Applications, you can set PDF files to 
"Always ask," "Save," or "Use <Application Name>".  If a file type is 
set to always save it to disk, you probably won't get the pop up you 
mention, because no application is going to try to open it vs saving to 

Most files COULD be opened, instead of saving to disk.  What info might 
be leaked to compromise (in some way) anonymity, depends on the app & 
how it's configured, if it is configured to use the Tor network as a 
proxy, how well it handles using it, etc.  I think most would agree, 
while using Tor, it's safer to save the file to disk, then open it.  
Depending on WHAT type file, maybe opening / running it after closing 
Tor.  Especially if not d/l from a known, trusted site & you're not 
absolutely sure what the file is & does.  Others may have more insight 
on specifics of this.

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