Earlier last week, it was revealed that a number of popular Netgear routers had exploitable security holes that made it possible for someone to take control of your network. Now, that hole has been patched up, but you'll need to update your firmware.
Depending on which router you have, you'll need to download a different firmware. You'll find the download and instructions over on Netgear's support pages, just click the link for your model:
Once you update your firmware, you should be in the clear. Head over to Netgear's article on the vulnerability for more info about your specific router.