When installing the TeamViewer.deb spying-on-your-paswords software (was sold for 1 billion dollar) it will autostart a service in the background that will allow others to connect to your machine.

if you only want outgoing connections (to your server, client, customer) you can disable the service like this:

sudo teamviewer --daemon disable; # disable teamviewer service

# it outputs the following
Tue Dec 22 13:14:41 CET 2015
Action: Removing ...
systemctl stop teamviewerd.service

kill '/opt/teamviewer/tv_bin/script/teamviewer' - root (/root/.local/share/teamviewer11 / /root/.local/share/teamviewer11)

Removed symlink /etc/systemd/system/graphical.target.wants/teamviewerd.service.