In Korea, all the tenants(*foreigner also) are protected from bad landlords by the HOUSING LEASE PROTECTION ACT. However, landlords cannot be protected from bad tenants by any law. Therefore, Korean landlords tend to require a large sum of deposit as insurance to protect their rental rights by themselves.
However, in the case of short-term contract available properties only requires the deposit as same as one month rent but the rent price is 20%~40% higher than more than year-long contract properties.