Tor uses swap?

Mike Perry mikeperry at
Wed Jan 5 21:57:22 UTC 2011

Thus spake andre76 at (andre76 at

> I'm running Ubuntu 10.04 and Tor browser bundle with scripts forbidden.
> Does any of my web search results or web pages (or anything else during
> the web session) I look at get sent to or put on the SWAP partition of
> my machine?

This is a good question. Tor has a torrc option that is off by default
to disable all swap activity *by the tor process itself*:
'DisableAllSwap 1'.

However, this is not all you need. Your web browser can still be
swapped arbitrarily to disk. Unfortunately, this is difficult for us
to control for two reasons:

1. It is not possible to access the system calls relevant to this from
Torbutton until Firefox 4 (which provides JS-Ctypes to addon
developers) is in common use.

2. Even if we do this with a custom TBB build, most operating systems
require root/administrator priviledges to disable swap activity. 

The other alternative is to set up encrypted swap. The Ubuntu
documentation on encryption is pretty sad and disorganized:

But I think there should be an option to set up encrypted swap during
the installation process. There certainly is on other modern distros
like Fedora and even CentOS.

> That is to say- is there any data on my computer I should shred after a
> Tor session?  (yes, I understand other than what I knowingly download
> like a PDF or music)

Other than swap, Torbutton should be blocking all history writes by
Firefox in Tor mode by default.

Mike Perry
Mad Computer Scientist evil labs
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