Lay a small piece of thread, or dental floss in the crack between the door and the jamb, or even across the knob. When you come back, and the thread is no longer where you left it, you'll know someone used that door.
Set a booby trap
Place a glass of water on the ground so that if the door swings open, the water will spill. Ideally, you have a rug or mat that will take longer to dry, so the intruder can't just clean up the mess and reset the trap before you return.
Belt or Rope
A belt or piece of rope also is a good option for securing an outward-opening door because the tether can be attached to a heavy object, like a refrigerator or couch. For French doors, wrap both handles with the tether, blocking them from opening.
For a door that opens out, build a wall by stacking desks or propping a table up in order to block the intruder's ability to see inside the room once the door is opened. For a door that swings in, push heavy furniture against it, prop a chair under the handle or use door jams.
The Smart Stop Hinge-Pin Doorstop attaches to any standard residential door hinge in seconds. This innovative product stops the door at the hinge, preventing damage to the walls, door, or molding. This steel doorstop has a decorative bright brass finish that complements most home decors.
get a small piece of paper and tape it to your door or door frame, in such a way that you can put it in a position, and when the door is opened and closed again it goes to a different position. Put something behind the door in a marked place, then when it moves you'll know someone has been in. change the locks?
For Android phone
Unfortunately, there is no direct way to check if the camera or the microphone of your Android device is being accessed. However, there is a workaround for it. Android users can download an app called Access Dots from the Google Play Store which will notify users the same way iPhone does.
Signs Your Lock Was Tampered With
If you suspect your lock has been tampered with, start with looking for these common signs: Brute force. Signs of brute force include bent deadbolts or latches, warped doors or door frames, and the presence of small paint circles caused by moving the locking fixture.
Once you've confirmed that your door is locked, take a look at who's at your front door by looking through a peephole, a window, or checking your doorbell or front door security cameras. A doorbell camera or a security camera pointed at your front door is probably the best way to check to see who's outside your house.
To evade the entity, players must avoid direct eye contact with the Eyes by either looking downward or in the opposite direction. Opening the door to the next room causes the eyes to vanish.
Firstly flatten out a hairpin or a bobby pin then put a blob of superglue on the end of the bobby pin. Carefully insert it into the keyway so that bobby pin can reach the pins or waffers at the back of lock lift the bobby pin up and smear the glue on the pins (repeat a couple of times).
Convex lenses are used in peepholes of house doors for security to provide a view of people or objects outside the doors.
The most obvious signs your lock has been tampered with are visible dents and scuff marks around the key hole. While these are quick and easy to notice, here are specific signs of lock tampering that you can look for and measures you can take to help prevent unauthorized entry.
Slip a small piece of paper between the door and sill. If necessary, fold it to get a tight fit. If you return and the paper is on the ground, the door has been opened.
Motion detection and optical sensors
Nowadays, most automatic doors operate with motion-detecting sensors. The majority of motion detectors use either microwave pulses or passive infrared (PIR) sensors to detect movement.
Sometimes referred to as a door screecher, the DorWatcher is an alarm unit used to prevent doors being left open for extended periods of time.
They each have slightly different features and use cases. Lockwatch is a great free option that doesn't have any annoying ads. Third Eye won't do much in the case of theft, but will catch prying friends. And CrookCatcher lets you see the photos both in-app and by email, making it a good all-around choice.
Use a Radiofrequency Scanner
If you've found something that looks like a bug, or you want to search for a listening device covertly, you can purchase a radiofrequency scanner. These pick up anything broadcasting a radio signal, including bugging devices.
Code to check if phone is tapped: *#21# Code to show unknown connections and tracking (for Android): *#*#4636#*#* or *#*#197328640#*#* Code to show unknown connections and if someone is tracing you (for iPhone): *3001#12345#*