1. A method of detecting camera tampering from at least one image captured by at least one camera, the method comprising: performing at least one of following operations: (i) detecting a size of a foreground region in an image, and determining whether a first condition, that the size exceeds a first reference value, is satisfied; (ii) detecting change of a sum of the largest pixel value differences among pixel value differences between adjacent pixels in selected horizontal lines of the image, according to time, and determining whether a second condition, that the change lasts for a predetermined time period, is satisfied; and (iii) adding up a plurality of global motion vectors with respect to a plurality of images, and determining whether a third condition, that a sum of the plurality of global motion vectors exceeds a second reference value, is satisfied; and determining that camera tampering has occurred if the first condition is satisfied when operation (i) is performed, if the second condition is satisfied when operation (ii) is performed, and if the third condition is satisfied when operation (iii) is performed.