I went through the experience at Canadian Customs a month.

The officer made me log in to Windows and then did a quick search for pictures, with me present.

He didn't notice the linux partition nor my encrypted directory (empty at the time). Changing the file extensions would have screwed up his search too.

They managed to catch a child pornographer the week before with this basic search. Amazing.

I filed an incident report with our security department when I got back.