title: What is the worst case when the epmd port is open?
body: <p>When using Erlang programs like <a href="http://www.ejabberd.im/" rel="noreferrer">ejabberd</a> the <a href="http://linux.die.net/man/1/epmd" rel="noreferrer">Erlang port mapper daemon</a> <code>epmd</code> is started and opens port <code>4369</code>.</p>
  
  <p>This port is accessible over the internet (only most recent ejabberd versions allow to configure that epmd should bind to localhost) by default.</p>
  
  <p>The ejabberd documentation recommends <a href="http://www.process-one.net/docs/ejabberd/guide_en.html#htoc81" rel="noreferrer">blocking this port via packet filter rules</a> and a <a href="http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=585122" rel="noreferrer">comment in the Debian bug tracker</a> calls this default behavior 'a nightmare from a security point of view'.</p>
  
  <p>What is the worst case scenario when ejabberd is running and port <code>4369</code> is not blocked?</p>
  
  <p>Say - the firewall is mis-configured by accident or something like that.</p>
  
  <p>What would be the most evil thing a Erlang-fluent attacker could do over this port?</p>
  
  <p>Under what user/privileges runs the <code>epmd</code> under a linux distribution (e.g. Debian/Ubuntu)?</p>