Comment 2 for bug 662791

I created a little workaround for this problem.

To apply:

sudo -s
cat <<_EOF_>/etc/rsyslog.d/49-modemmanager-workaround.conf
# Workaround for bug from modemmanager spamming the logs
# https://bugs.launchpad.net/ubuntu/+source/modemmanager/+bug/662791

:msg, contains, "Duration: " ~

& ~

:msg, contains, "Access Technology: " ~

& ~
_EOF_
service rsyslog restart

This will prevent modemmanager writing these two types of messages to any log. Works for me at least.