Yes, airport security (such as the TSA) can and will open your checked baggage if it flags an anomaly during the X-ray or CT scan. This is a standard part of the security screening process. If your bag is selected for a physical inspection, officers will open it to verify the contents. If you use a lock that is not "TSA-approved," security officers are authorized to break or cut the lock to gain access, and the airline or airport is not liable for the damage. If you use a TSA-approved lock, they can use a master key to open it without damage. After a physical search, the TSA is required to place a "Notice of Baggage Inspection" inside your suitcase to inform you that it was opened. In other countries, policies vary; some may require you to be present if a bag needs to be opened, but in the U.S., UK, and much of Europe, the search is conducted behind the scenes to keep the luggage moving through the automated sorting systems.