mastoer32.dll is a worm W32.Katomik-A. mastoer32.dll spreads via open network shares. Related files: %Windows%\AtomicpartC.exe %Windows%\K-set.bmp %System%\Atomic-x27.exe %System%\mastoer32.dll More info: http://www.sophos.com/virusinfo/analyses... Removal: Remove mastoer32.dll from Windows startup using antivirus (also check How To Remove section)Startup Optimizer.