Systems, methods, and apparatus are disclosed involving a door blocking apparatus to reduce a likelihood of, and possibly prevent, opening of a door by unauthorized personnel. The apparatus may be networked in a security system and may be connectable to an online security platform. In a particular embodiment, an embodiment of the invention may include a security system involving a plurality of door locations having a plurality of networked door blocking apparatus. Each door blocking apparatus may include a door blocking mechanism operable by a user on a safety side of a door, such as having the user rotate an apparatus handle that rotates the door blocking mechanism between a non-blocking position and a blocking position. In the non-blocking position, the door blocking apparatus does not block the door from opening and closing. In the blocking position, the door blocking apparatus blocks the door from opening and from closing completely.