The old dirty trick which works until a new update is released (which is like every week with Nintendon't these days) is to hold UP+LT+RT+A while pressing POWER to turn on the 3DS. Keep holding them until the update screen appears. Click continue and then another UELA screen appears. THIS IS WHERE YOU CLICK "DO NOT ACCEPT" OR YOU WILL ACCIDENTALLY UPGRADE YOUR SYSNAND TO LATEST FW!!!! It will kick back out to sysNAND and won't bother you until Nintendo gets antsy and farts out another one.
Yes, your fingers will get a yoga stretch. Yes, it's like staring into the mouth of FW death. Yes, you must repeat this the next time Nintendon't farts out another "security improvement" update.
Most ppl just avoid doing this all together. Or they go the extreme route of blocking DNS'.
Does blocking DNS' affects your Homepass router???