Não sei se é isso o que você está procurando, mas ele fornecerá um "modo de privacidade". Estou citando webupd8.org :
Until Zeitgeist Global Privacy is released, install Activity Journal (don't use the version in the official Ubuntu 11.04 Natty Narwhal repositories - that doesn't seem to work), go to its Preferences and on the Plugins tab, enable "Blacklist Manager" (seems you have to double click the checkbox to enable it) - now a new "Blacklist" tab should be displayed. Here, click the add button and enter the path to your private files (porn). If you want to block all files, use "*" for the path.
You can also clear the Zeitgeist history (this is the history of recent files that's display in Dash) by using the following commands:
rm ~/.local/share/zeitgeist/activity.sqlite zeitgeist-daemon --replace