Displays a dialog with three checksums to prevent the installation of malware

verifyChecksum.sh

osascript <<EOT
display dialog "MD5:
$(openssl md5 $1 | awk '{print $2}')

SHA1:
$(openssl sha1 $1 | awk '{print $2}')

SHA256:
$(openssl dgst -sha256 $1 | awk '{print $2}')" with title "$(basename $1)" with icon Caution
EOT

Linking to where you discussed using this gist with something like Hazel.

http://jacobsalmela.com/prevent-ransomware-by-automatically-finding-the-checksum-of-downloaded-files/