Images in print media represent a series of overlapping dots that should create an illusion of more colors. When you scan such a photo you can usually discover a moire pattern. A moire pattern results from incorrect screen angles of overprinting halftones.
You can try to avoid moire at the scanning stage. Sometimes a well-chosen scan angle can produce a remarkable effect. However, if you deal with a scanned image you have only one method of the moire suppression at your disposal - apply image processing techniques.
On the photo below you can see a scan of a music CD cover. Moire is visible.
Noise Buster will process the image using the Automatic Filtering preset from the list of presets. The program will analyse the noise on the whole image, create histograms for the noise, and offer settings for the parameters Noise Level and Smooth Level for every noise type.