There have been reports in the past that some virus scanners claim that the Emacs distribution has a virus. This is extremely unlikely if you have downloaded Emacs from the GNU FTP site or one of its mirrors and the GPG signature for it is valid and listed in the GNU keyring, unless perhaps it is a new release made in the last few days, in which case you should exercise more caution and report the problem. Past problems seem to have been caused by virus checkers running into a buffer size limit when unpacking large tar.gz files for scanning, and reporting the failure as an “unknown virus”.