One of the best open source anti-virus for Mac OS X is ClamAV by Cisco. ClamAV is a crossplatform open source anti-virus with high performance, it is also the open source standard for mail gateway scanning software.

The most easy and efficient way to install clamAV on OS X is using homebrew brew install clamav Before you could scan any file, first do the following: Under /usr/local/etc/clamav

cp freshclam.conf.sample freshclam.conf
cp clamd.conf.sample clamd.conf

and comment out following lines in both files:

# Comment or remove the line below.
# Example

and add the mirror line to clamd.conf:

DatabaseMirror database.clamav.net

Then run: freshclam to update the database

Now, you could use clamscan -r --bell -i /path/to/file to scan the file, where:

    --help                -h             Show this help
    --version             -V             Print version number
    --verbose             -v             Be verbose
    --archive-verbose     -a             Show filenames inside scanned archives
    --debug                              Enable libclamav's debug messages
    --quiet                              Only output error messages
    --stdout                             Write to stdout instead of stderr. Does not affect 'debug' messages.
    --no-summary                         Disable summary at end of scanning
    --infected            -i             Only print infected files
    --suppress-ok-results -o             Skip printing OK files
    --bell