A landlord is supposed to provide secure locks to your apartment when you move in. That means changing the locks from the previous rental, and giving you a new set of keys. If the landlord fails to change the locks and your apartment is burglarized, you can sue for damages. You'll have to prove it caused the theft and establish the value of the stolen property. The problem is that if you sue, and your lease is unregulated, the landlord is not likely to renew it. You may be able to defend against eviction by claiming the non-renewal is retaliation for asserting your rights, but then you will be involved in two lawsuits. Depending on the language in your lease and how a judge rules, you may not get reimbursement of your legal fees. A better solution is to ask the landlord if you can add your own locks, and supply the building's management with a set of keys, if they require it.