There's various types of spam, one are viruses posing as mp3's or wma's, and another are deliberately corrupt files. mp3 Bit-Rates Versus File Sizes. If you have a rough idea how large a music file should be according to its bitrate & you see a file with a size that does not match what would be expected for the bit rate, then chances are it's a deliberately corrupt file.

Other than that, LW's media player is not that good anyway & gets low cpu attention compared to LW's main functions of uploading & downloading, etc.