If the brokerage is a member of the Securities Investor Protection Corporation (SIPC) then your funds are protected up to $500,000, with a limit of $100,000 for cash balances. SIPC members will usually display their membership on all advertisements, brchures, etc. Since most SIPC members are also members of the National Securities Dealers Association (NASD) you may see it rendered “Member NASD/SIPC”. Some brokerage firms offer separate protection over and above the SIPC limits, usually through a surety bond.
If the brokerage does not offer the protections above, then you’re on your own with other claiments in bankruptcy court.