If you're a small business and you get targeted by a larger company with more funds, I'm sorry to say but there's very little you can do. Litigation is very costly and can be stretched out for years and years during which you will bleed cash and most likely fail. You might try to get a credit line but banks don't lend cash to small companies that are being sued and they are right to do so.

However, one thing your competitors can't steal is your personality. Become the face of the company, do LOTS AND LOTS of PR, stamp your face everywhere you can. Even if your competitors replicate your design to the smallest unit, they will only be able to target people that are strapped for cash and look for alternative which inherently isn't the market you want to target. It's better to have an established niche market with a small but consistent customer base that won't jump ship when they see someone selling a similar good or a service. To put it short, position yourself in a way that the cost of switching is very high and is not tied to the product or the service.

Good luck!