A method for determining when a break-in attempt is in process, the method being performed in a break-in determiner and comprising the steps of: determining that a first vibration condition is true when a vibration parameter associated with a barrier is greater than a first threshold, wherein the first vibration parameter is obtained from measurements from an accelerometer; determining whether an acceptable activity condition is true or not, such that the acceptable activity condition is true only when there is an auxiliary signal indicating acceptable activity, comprising determining that the acceptable activity condition is true only when a time difference between determining that the first vibration condition is true and receiving the auxiliary signal is less than a threshold duration; and determining that a break-in attempt is in process when the first vibration condition is true and the acceptable activity condition is false characterised in that the auxiliary signal is one or more of: a lock action signal received from an electronic lock associated with the barrier, the lock action signal indicating that a valid locking or unlocking action is occurring; a bolt action signal received from a bolt sensor associated with the barrier, the bolt action signal indicating that a bolt associated with a lock of the barrier is moving; a latch action signal received from a latch sensor associated with the barrier, wherein the latch action signal indicates that a latch associated with a lock of the barrier is moving; a sensor signal received from a touch sensor of a handle on the inside of the barrier, the sensor signal indicating that a person touches the handle; and a barrier sensor signal received from a barrier sensor indicating a detection of when the barrier is open or closed and/or when the barrier transitions between the open state and closed state. determining that a first vibration condition is true when a vibration parameter associated with a barrier is greater than a first threshold, wherein the first vibration parameter is obtained from measurements from an accelerometer; determining whether an acceptable activity condition is true or not, such that the acceptable activity condition is true only when there is an auxiliary signal indicating acceptable activity, comprising determining that the acceptable activity condition is true only when a time difference between determining that the first vibration condition is true and receiving the auxiliary signal is less than a threshold duration; and determining that a break-in attempt is in process when the first vibration condition is true and the acceptable activity condition is false characterised in that the auxiliary signal is one or more of: a lock action signal received from an electronic lock associated with the barrier, the lock action signal indicating that a valid locking or unlocking action is occurring; a bolt action signal received from a bolt sensor associated with the barrier, the bolt action signal indicating that a bolt associated with a lock of the barrier is moving; a latch action signal received from a latch sensor associated with the barrier, wherein the latch action signal indicates that a latch associated with a lock of the barrier is moving; a sensor signal received from a touch sensor of a handle on the inside of the barrier, the sensor signal indicating that a person touches the handle; and a barrier sensor signal received from a barrier sensor indicating a detection of when the barrier is open or closed and/or when the barrier transitions between the open state and closed state. a lock action signal received from an electronic lock associated with the barrier, the lock action signal indicating that a valid locking or unlocking action is occurring; a bolt action signal received from a bolt sensor associated with the barrier, the bolt action signal indicating that a bolt associated with a lock of the barrier is moving; a latch action signal received from a latch sensor associated with the barrier, wherein the latch action signal indicates that a latch associated with a lock of the barrier is moving; a sensor signal received from a touch sensor of a handle on the inside of the barrier, the sensor signal indicating that a person touches the handle; and a barrier sensor signal received from a barrier sensor indicating a detection of when the barrier is open or closed and/or when the barrier transitions between the open state and closed state.