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.