According to this article at Ars Technica, routers supplied by a number of European Internet providers leave an open port that would allow outside access. The reason for the open port was probably so that the ISPs could perform maintenance and upgrades. An unintended consequence is that attackers could exploit this open port to do bad things. Attacks on “Internet of Things” is one exploit that seems to be happening.
The port in question is 7547. If you manage your own router, you may want to check if this port has been left open or not. Router manufacturers such as Linksys, D-Link and Netgear are not mentioned (Zyxel and Speedport are mentioned) but it wouldn’t hurt. At the very least, I hope you aren’t still using the default manufacturers password for your router. Given the large number of routers out there (and not wanting to specify which one I use) the only advice is to “Read your manual”.