The Distributed Checksum Clearinghouses or DCC is an anti-spam content
filter that runs on a variety of operating systems. The counts can
be used by SMTP servers and mail user agents to detect and reject
or filter spam or unsolicited bulk mail.  DCC servers exchange or
"flood" common checksums.  The checksums include values that are
constant across common variations in bulk messages, including
"personalizations."

Note that this installs three setuid binaries in /usr/bin.