A portable perimeter defense system is provided that is configured for preventing unwanted intrusions by vehicles or other heavy and fast-moving vehicles into a protected area while also providing requisite ballistic resistance capabilities. The defense system includes individual modular barriers that can be readily transported to a point of use and can be secured in place without requiring heavy equipment or power sources, such as electricity. This can be readily achieved with as few as one person. The modular barriers include a front plate configured to provide exceptional ballistic protection in the direction of impact and to provide an impact surface capable of withstanding impact. When circumstances warrant a double row portable perimeter defense system, a bracing system is provided to render parallel rows of barriers cooperative to prevent aft tilting of the impacted forward barriers. The bracing system transfers an impact force against the forward barrier rearward and downward toward a base plate of the rearward barrier. A method of protecting an area with a portable perimeter defense system and method of installing a portable perimeter defense system is also provided.