The IRS can freeze a bank account by placing a levy. A judge's approval is not required. A levy only attaches to the money in the account on that day up to the amount of the levy. The bank is required to hold the money for 21 days prior to sending it to the IRS. This allows you to have the levy released and make alternate payment plans. You will have been given a Notice of Intent to Levy 30 days prior to the levy going into effect.
As to the safety deposit box, the contents are property. The IRS can place a lien on all your property. A lien is different than a levy. Unless the IRS new of the safety deposit box and/or the contents, I am unsure of your concern. After receiving no answer from a taxpayer to the multiple notices sent, the IRS would place a levy and see if they can get money that way prior to other collective actions, such as liens or seizures.
IRS Resolution can be handled by an attorney licensed in any state, but I suggest that you speak to an experienced tax attorney.
Anastatia Quirk Ellis, Esq. is licensed to practice law in Florida, Massachusetts and U.S. Tax Court, This answer is provided as general information and does not initiate an attorney-client relationship.
Anastasia Ellis's answer is on point. They would have had to notify you of a lien by way of Notice of Federal Tax Lien. If that happened, which is likely, it would attach to any property the IRS is aware of. You probably, as a practical matter, could still access the box.
The "Freeze" or "Levy" is a request by the bank to take your cash from the bank account, which is a different procedure. This can happen at any time. But, the levy, which will be paid out after 21 days must be done on notice and the bank has a 21 day grace period in which you can try to work it out.