W32/Nimda-B is a variant of the commonly encountered W32/Nimda-A executable file virus.
W32/Nimda-B uses the filenames PUTA!!.SCR and PUTA!!.EML in place of README.EXE and README.EML used by the original W32/Nimda-A.
The virus executable file has also been compressed in an apparent attempt to avoid detection by anti-virus products.