You can do a few things to increase security:

1. Disable remote administration
2. Use strong passwords - Changing as often as you feel is needed
3. Make sure your router is up to date and still under support. If not, you could be vulnerable
4. Enable MAC address filtering, if supported by your router

You can do a few things to increase router security:

1. Disable remote administration - Only people inside your network can change it's settings
2. Use strong passwords - Changing as often as you feel is needed
3. Make sure your router's firmware is up to date and still under support. If not, you could be vulnerable to exploits
4. Enable MAC address filtering - If supported by your router, only known MAC addresses can connect to it