This method requires no software, no fancy router settings/models, and doesn't affect any other devices on your network. It works in sleep mode, too. 1. On your PC, go to OpenDNS.com and start up a free account: https://www.opendns.com/ 2. add a network and use the default IP that shows up: https://dashboard.opendns.com/settings/ *This is your modem's IP, not your PC's IP. you can double check at http://www.whatismyip.com/ 3. Click your IP address as it's listed to go to your CONTENT EDITING page. Keep the categories set at NONE but add these individual domains near the bottom to block: nus.c.shop.nintendowifi.net nus.cdn.c.shop.nintendowifi.net nus.cdn.wup.shop.nintendo.net c.shop.nintendowifi.net nus.wup.shop.nintendo.net nus.cdn.shop.wii.com (*may prompt a "block entire content delivery category?". Choose No/Domain only.) 4. On your 3DS: System Settings > Internet Settings > Connection Settings > Connection # > Change Settings > DNS > Auto-Obtain NO > Detailed Setup 5. Set Primary DNS to 126.96.36.199 and secondary to 188.8.131.52 6. Enjoy life In case it's not working: Are you using another DNS? If you have a custom DNS (such as google DNS) setup on your router, this might not work. You can clear the router's DNS settings and set up Google DNS on your PC to keep using GoogleDNS with your computer, and OpenDNS from your 3DS. Be sure to disable any proxy or VPNs for Step 2. Don't know if you have one? http://www.whatismyip.com/ will tell you if it detects a proxy, and if it's giving you incorrect location/ISP details, you might be running a VPN/proxy. You might have a Dynamic IP (a home IP/step 2 IP that changes once in a while). OpenDNS has documentation on how to deal with this.' OpenDNS only offers one free IP setup per account. If you connect to another router OpenDNS won't be able to block the request. (I will explain why this happens in more detail later) Disclaimer: I know a thing or two about routers, but it is a hobby, not a profession. I might be wrong about the domains blocked. I appreciate any input to make this right in case I'm wrong. So far I haven't been pinged to update, but I also haven't tried to force the update check either. If anyone knows for certain what domain to block, please let us all know so I can edit this post. If the 3DS pings an IP instead of a domain, this OpenDNS method is worthless, but apparently that's not the case so we should be okay. Spotpass/Streetpass/Homepass Warning: Spotpass will ping the update. Because spotpass hotspots are preconfigured into every 3DS, it will not use OpenDNS. This method will not protect you from downloading the update over spotpass. Also, this is just speculation. Feel free to confirm/disprove this for the rest of us. Homepass can be configured to use OpenDNS, but it's not something I'm going to get into because there are too many unique ways to homepass.