Setting up a phone for a parent who is a new internet user
Twenty minutes of setup removes most of the attack surface. A checklist you can work through on someone else's phone this weekend.
Turn off installation from unknown sources
Almost every serious fraud involving a phone requires an app that did not come from the Play Store or App Store. Disabling sideloading blocks the loan apps, the fake trading apps and the remote-access tools in one setting.
On Android this sits under Settings, Apps, Special app access, Install unknown apps. Set every entry to not allowed.
Remove screen-sharing apps
AnyDesk, TeamViewer, QuickSupport and similar tools have almost no legitimate use on a personal phone. If one is installed and nobody can explain why, remove it.
Explain the rule in one sentence: nobody who calls you should ever need to see your screen.
Set a transaction limit
Most banking apps let you cap daily UPI and net-banking transfers. Setting this to a realistic weekly need converts a catastrophic loss into a survivable one.
Raising the limit takes a few minutes when it is genuinely needed, and those few minutes are exactly the pause a fraudster cannot afford to allow.
Agree on one phone call
Decide together that any request for money, however urgent and whoever it comes from, gets one call to you before anything is transferred.
This single habit defeats digital arrest, romance fraud, the fake-relative call and most task scams, because all of them depend on the victim not talking to anyone.