One of the key reasons policymakers and law enforcement agencies find 3D printed guns worrisome is their so-called "untraceable" nature, but researchers may have found a way to match a gun to a printer.

Unlike traditional firearms, 3D printed guns have no bills of sale or serial numbers, nor do builders go through background checks. Researchers at the University of Buffalo, however, have discovered that each 3D printer leaves its own signature. The researchers have dubbed this a "hardware fingerprint."

These hardware variations in each printer create a pattern on each object printed. Even two printers of the same make and model have a slightly different fingerprint.

The researchers are calling the identification system they developed "PrinTracker."

"Two human beings can write the same thing, but they'll have different handwriting. It's the same concept for [tracking] 3D printers," Wenyao Xu, lead author of the paper told CNET.

The controversy surrounding 3D printed guns started in 2013 with a long legal battle between the State Department and Defense Distributed, the organization that posted gun schematics online. State argued publishing the plans violated International Traffic in Arms Regulations, but the parties came to a settlement earlier this year that allowed Defense Distributed to publish the plans. Other litigation is underway to prevent the spread of 3D printed firearms, such as new California state law that would require background checks to purchase ammunition.

The researchers believe that PrinTracker could also be used to track down counterfeit items made using 3D printing, in addition to firearms.