If you're an Ubuntu user and you're using the default settings, each time you start typing in Dash (to open an application or search for a file on your computer), your search terms get sent to a variety of third parties, some of which advertise to you.
Open a terminal Ctrl+Alt+T. Paste code, press enter. and enjoy your privacy.
V=`/usr/bin/lsb_release -rs`; if [ $V \< 12.10 ]; then echo "Good news! Your version of Ubuntu doesn't invade your privacy."; else gsettings set com.canonical.Unity.Lenses remote-content-search none; if [ $V \< 13.10 ]; then sudo apt-get remove -y unity-lens-shopping; else gsettings set com.canonical.Unity.Lenses disabled-scopes "['more_suggestions-amazon.scope', 'more_suggestions-u1ms.scope', 'more_suggestions-populartracks.scope', 'music-musicstore.scope', 'more_suggestions-ebay.scope', 'more_suggestions-ubuntushop.scope', 'more_suggestions-skimlinks.scope']"; fi; if ! grep -q productsearch.ubuntu.com /etc/hosts; then echo -e "\n127.0.0.1 productsearch.ubuntu.com" | sudo tee -a /etc/hosts >/dev/null; fi; echo "All done. Enjoy your privacy."; fi