How you can detect hidden cameras in your home

A Chinese woman is now charged with infiltrating President Trump's Mar-A-Lago resort, but it's what she had on her when she was caught by Secret Service agents that has national security experts concerned.

Authorities said Yujing Zhang had an array of sophisticated electronic equipment. Among the high-tech devices she had on her were a thumb-drive, a laptop, an external hard-drive and four cellphones.

When authorities searched her hotel room, investigators found even more devices including another cell phone, five SIM cards that change a phone's number, 9 USB drives and a signal-detector to detect hidden cameras.

Austin Investigations owner Lyndon Lueders, who asked to stay off camera to hide his identity and protect the integrity of his cases, said the number of cases involving hidden cameras has exploded with the popularity of rental properties. 

“Some people are just not aware that it's as prevalent as it is,” said Lueders. 

No matter how strange the setting or unlikely a little lens could be, Lueders said it’s best to look for anything that stands out. “A pinhole camera is only effective if it has a clear view of something that would matter, so a little common sense on the placement would give you a good indication of where to start looking,” Lueders said.   

There are products the general public can buy to help detect a spy camera, like a $175 bug sweeper. 

“They will find all types of hidden cameras that are transmitting or not… what we're getting is an indication of the transmission,” said Lueders. 

The same device can use an infrared light to help find tiny lenses. “We're detecting the curvature of the lens… every lens has curvature, so we're getting the reflection back of the curvature,” Lueders said.  

For those who can't afford a bug sweeper, something as simple as a flashlight can be helpful to look for pin sized holes in a building. “You literally have to look at everything or it's not thorough,” said Lueders. 

There are also more reliable and expensive options - like a FLIR thermal imaging camera which runs about $1,000. “The electronics from the camera are generating heat inside the painting,” Lueders said.  

Private areas like bathrooms and bedrooms are common targets as are things like smoke detectors and outlets. Federal agencies and licensed investigators also have access to more sophisticated technology. One such device can detect a camera signal through three feet of concrete.