.EFW File Extension
File TypeRenamed Zip or Executable File
What is an EFW file?
EFW zipped files may be opened by changing the file extension to ".zip" and opening the file with a decompression utility, such as WinZip or Stuffit Expander. Executable files may be run directly by changing the file extension to ".exe" and opening the file.
NOTE: Do not open unknown e-mail attachments from non-trusted sources, as they may contain viruses or other malicious programs.
You can prevent EFW files from being created by temporarily disabling your antivirus software when downloading legitimate zipped or executable files.