Question about blocking system updates

Hi, I see a loooot of information about this, but mostly old posts, so I need to you confirm my idea:

to block system updates on my 3DS (and my WiiU too?) I just need to add the following domains to the deny filter in my home router?

• nus.c.shop.nintendowifi.net
• nus.cdn.c.shop.nintendowifi.net
• nus.cdn.shop.wii.com
• nus.cdn.wup.shop.nintendo.net
• nus.wup.shop.nintendo.net

I am making some basic homebrew, so I want to use FTBrony to send the binary to the SD, and...

Question about blocking system updates