Legal Question in Landlord & Tenant Law in Illinois

Frankly that's not much security in today's world. Plus, a lot has to do with how the burgler got into YOUR apartment. I assume you have to have a key to get into your apartment, and if there are windows and sliding glass doors to the outside (maybe a patio or balcony) they should have locks and you would be responsible for making sure they were locked while you were out. Assuming there is any maintenance staff and they have keys, access could be an issue. But ultimately it has to do with whether or not the landlord knew or had reason to know that these security measures were not adequate because there had been other incidents, of that the landlord may have had a bad egg on the maintenance staff who was going into units, which could make the landlord "negligent". Finding out if there was negligence, is often difficult unless there are police records or insurance claims or other evidence (including other tenants having been burgled in a similar way or having seen something like a maintenance person going into your apartment.....).

You need to look at your lease no matter what. Most leases say that unless the landlord is negligent, it is not responsible for these kinds of things AND your lease may make you responsible for getting "renter's insurance" to protect yourself. If you had renter's insurance you should think about filing a claim and then let the insurance company investigate and decide if they want to sue the landlord for what they had to pay you as a claim. If you did not have renter's insurance, or your insurance company denies your claim (they may be able to if you left the lockable front door, windows or sliding glass door to the outside unlocked and so there was no real "break-in"), you may be stuck seeing if the landlord will accept a claim against its own insurance (generally landlords won't want to) or filing a lawsuit. But if you have to file a lawsuit again beware of the obstacles pointed out above.

Finally, since I have none of the particulars of this situation, and I do not have your lease to review, you should talk to an attorney and, if you had renter's insurance, your agent. For sure.