Installing DCC
See InstallingDCC.
Using DCC
DCC is the Distributed Checksum Clearinghouse. http://www.rhyolite.com/anti-spam/dcc/ . DCC is a HashSharingSystem.
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loadplugin Mail::SpamAssassin::Plugin::DCC |
It is recommended to set explicit configuration in your "local.cf", so things are not relying on PATH etc.
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use_dcc 1
# When using dccifd, socket will be search from dcc_home
dcc_home /var/dcc
dcc_timeout 8
# If not using dccifd, dccproc is used
dcc_path /usr/local/bin/dccproc
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I've installed DCC but I never seem to get DCC hits, even though I should. Why?
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Check your firewall setup. DCC uses UDP packets when replying, which are blocked by most firewalls by default. As a result, it requires that you open your firewall for DCC reply packets on UDP port 6277. Here's sample firewall rules required:
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allow udp local gt 1023 to remote 6277
allow udp remote 6277 to local gt 1023
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Modern firewalls already track connections and replies, so simply having a standard rule like "iptables -A INPUT -m state --state ESTABLISHED,RELATED -j ACCEPT" is enough. For more information see: https://www.dcc-servers.net/dcc/FAQ.html#firewall-ports
If you're running a large site, processing upwards of tens of thousands of messages a day, the DCC maintainers have requested that you consider setting up your own DCC server as described in dccd(8), and arrange to peer with the rest of the public servers, to reduce their load.
IPTables Setup:
Assuming you allow all outbound packets out of your machine, you only need to add an INPUT rule to your /etc/sysconfig/iptables file. Add the following line in your INPUT chain, above any REJECT rules:
-A <chain-name> -p udp -m udp --dport 1024:65535 --sport 6277 -j ACCEPT
DCC does not give hits in spamd
If DCC gives hits when run with "spamassassin" from the command-line, but not from spamd, you may have a PATH issue where the DCC client cannot be found in spamd's path.
Add the path to your dccproc tool to the local.cf file:
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Detailed instructions
Very detailed instructions on configuring DCC for a personal Unix account are in SingleUserUnixInstall.
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