Deny Hosts¶

denyhosts (http://denyhosts.sourceforge.net) is a python script that acts as a dynamic blocker for SSH and other services. It monitors connection attempts and adjusts /etc/hosts.deny if too many failed connection attempts are made.

sudo apt-get install denyhosts

Sometimes valid connection attempts fail, and a user may end up being denied access to the host. In this case, the script unban below can be run by an administrator to revert the block imposed by denyhosts:

#/bin/sh
REMOVE=$1

/etc/init.d/denyhosts stop

cd /var/lib/denyhosts
for THISFILE in hosts hosts-restricted hosts-root hosts-valid users-hosts;
do
  mv $THISFILE /tmp/;
  cat /tmp/$THISFILE | grep -v $REMOVE > $THISFILE;
  rm /tmp/$THISFILE;
done;

mv /etc/hosts.deny /tmp/
cat /tmp/hosts.deny | grep -v $REMOVE > /etc/hosts.deny;
rm /tmp/hosts.deny

/etc/init.d/denyhosts start