Is it illegal for the company to cut off employees' social security privately?

If the company arbitrarily cuts off the social security of employees, which is an illegal act, the social insurance premium collection agency shall order it to pay within a time limit, and from the date of default, an additional fine of 5/1000 will be charged every day. Workers who unilaterally terminate the labor contract have the right to ask the unit to pay economic compensation. The economic compensation shall be paid according to the standard of one month's salary for each full year of the employee's working years in the unit.

legal ground

Article 86 of People's Republic of China (PRC) Social Insurance Law

If the employer fails to pay the social insurance premium in full and on time, the social insurance premium collection agency shall order it to pay it within a time limit or make up for it, and from the date of default, an overdue fine of 5/10000 shall be added daily; Failing to pay within the time limit, the relevant administrative departments shall impose a fine of more than one time and less than three times the amount owed.