It can be shown that as the speed of a body approaches the speed of light the approximation of momentum as p = mv becomes innacurate and its actual relativistic momentum must be used which is given by p = mv / root(1-sq(v/c)) . We can see that this approximates to p = mv at values of v<<c.
The above equation for relativistic momentum is sometimes interpreted to mean that a rapidly moving body undergoes an increase in mass.
relativisticmass =rest mass / root(1-sq(v/c))
And we can see that as v increases so does the relativistic mass and thus a larger amount of energy is required to increase the velocity further, indeed if the velocity were to equal c then the relativistic mass would be infinite and an infinite amount of energy would be required to take the velocity past c. Therefore to all intents and purposes we cannot travel faster than light.