You could download large binaries for only so long to cover your tracks, so I just ended up running a constant SSH session to a Lynx browser, so casual passersby would think I was working.
I quit about 6 months later for many other very good reasons, boredom being a huge one. A couple of months earlier I had asked if I could transfer to a new role (from developer to admin), which was flatly denied. When I announced I was leaving, one of the three senior management came up to me and said that in the last management meeting he had said I was bored and that they needed to find something more for me to do. Apparently he was shouted down (metaphorically).
The last I heard of the company was that as a result of my departure, they would no longer hire graduates with A grades. They would look for B or C grades from now on. I can't imagine a worse lesson to learn, but there you go.