Forbidden-region virtual fixtures (FRVFs) are traditionally imposed on users via proportional-derivative (PD) control. To reduce user penetration into the forbidden region, this paper proposes a new controller, hereafter called continuous impulsive force (CIF) controller. The CIF controller generates passive impulsive forces throughout users' motion into the forbidden region. These impulsive forces annihilate users' velocity into the forbidden region. Superimposed on typical PD control forces, the CIF control forces reduce users' incursion into the forbidden region, and render the feel of fully plastic collisions.