W32/Hasnot-A is a worm and companion virus for the Windows platform.

W32/Hasnot-A will hide files and folders, appending the original file or folder name to a copy of itself.

Once installed W32/Hasnot-A spreads through network shares and removable storage devices, including USB keys. W32/Hasnot-A copies itself to the root folder of the drive as Skynet.exe and adds an autorun.inf file.

More information can be found at this Sophos page.