What are the lagal and organisational requirements in relation to security and confidentiality?

i work in a barristers office as an admin assistant

This varies with the nation, industry, type of data on people.

There is information associatexd with our identity, that we need to give to an employer so the right taxes get paid, that we need to give to a financial institution, etc. Our employer has a fiduciary responsibility to keep the information about us confidential and secure.
Every business that has such info on us, neccessary to do whatever they do for us, financial, medical care, etc. has a fiduciary responsibility to keep that information in confidence, only shared with people who have a legally supported right to know or access the info. It may be stored in a computer. It may be stored in a file cabinet. However it is stored, it must be stored in a manner in keeping with certain security standards.

Sometimes two or more organiations enter into some kind of business deal. Typically from the outset some contract is drawn up in which the organizations agree to keep certain facts about each other confidential. Yje contract spells this out.

When we cross boundaries between businesses, government agencies, industries, nations, there are laws and contracts that also cross those boundaries. These laws are perpetually evolving. Most new laws are common sense, not all of them.