This paper investigates physical layer security (PLS) in a full-duplex (FD) system with movable antennas (MAs). The system consists of an FD base station (BS) equipped with multiple transmit and receive MAs, serving an uplink (UL) user and a downlink (DL) user. Each user operates in half-duplex (HD) mode with a single fixed-position antenna (FPA) and is eavesdropped by a single-FPA eavesdropper (Eve). To ensure secure communication, artificial noise (AN) is transmitted to obstruct Eve's interception. The main contributions of the paper are: 1. **System Model**: A detailed system model is proposed, including the channel responses and signal equations for UL and DL transmissions. 2. **Problem Formulation**: An optimization problem is formulated to maximize the sum secrecy rate (SSR) by jointly optimizing the beamformers and MA positions. 3. **Alternating Optimization (AO) Method**: An AO method is developed to solve the non-convex optimization problem by decomposing it into three subproblems and solving them iteratively using successive convex approximation (SCA), semidefinite relaxation (SDR), and particle swarm optimization (PSO). 4. **Simulation Results**: The proposed scheme is evaluated through simulations, demonstrating significant performance gains in SSR compared to benchmark schemes. The paper highlights the effectiveness of the proposed scheme in enhancing secure communication in FD systems with MAs, particularly in terms of SSR improvement.This paper investigates physical layer security (PLS) in a full-duplex (FD) system with movable antennas (MAs). The system consists of an FD base station (BS) equipped with multiple transmit and receive MAs, serving an uplink (UL) user and a downlink (DL) user. Each user operates in half-duplex (HD) mode with a single fixed-position antenna (FPA) and is eavesdropped by a single-FPA eavesdropper (Eve). To ensure secure communication, artificial noise (AN) is transmitted to obstruct Eve's interception. The main contributions of the paper are: 1. **System Model**: A detailed system model is proposed, including the channel responses and signal equations for UL and DL transmissions. 2. **Problem Formulation**: An optimization problem is formulated to maximize the sum secrecy rate (SSR) by jointly optimizing the beamformers and MA positions. 3. **Alternating Optimization (AO) Method**: An AO method is developed to solve the non-convex optimization problem by decomposing it into three subproblems and solving them iteratively using successive convex approximation (SCA), semidefinite relaxation (SDR), and particle swarm optimization (PSO). 4. **Simulation Results**: The proposed scheme is evaluated through simulations, demonstrating significant performance gains in SSR compared to benchmark schemes. The paper highlights the effectiveness of the proposed scheme in enhancing secure communication in FD systems with MAs, particularly in terms of SSR improvement.