http://pennysleuth.com/how-to-defend-your-portfolio-against-short-sellers/

"Shorts have the deck stacked against them – they have to pay to keep their positions open. If a company turns out quarter after quarter of good numbers, it’s not going to stay heavily shorted for long without incurring some major financial losses on those bets.

If you’re looking for stocks that are less disposed to short attacks, firms with low floats can be a good option. Because there are fewer shares trading, it costs short sellers a whole lot more to borrow shares to short, often making a bet against the stock uneconomical.

On the flip-side, low float stocks are also subject to bigger price swings…"