Please check that your brokerage has a security guarantee.
The following 4 brokerages offer a security guarantee.
- Fidelity
- TD Ameritrade
- ETrade
- Schwab
If a thief steals all your assets from one of the above brokerages and if you have not been negligent, then the brokerage will restore the value of your account.
Vanguard refuses to offer a security guarantee. If a thief steals all the money from your Vanguard account, Vanguard will not compensate you. You will lose everything.