10/17/2014 02:19 pm ET Updated Dec 06, 2017

Is the Creepiest Internet Stalking Tool Yet Right at Our Fingertips?

When Google quietly launched its new Search by Image function last June, the official suggested uses for the new service were fairly benign. Try searching "places, art, or mysterious creatures," the product description still suggests. To do that, you simply drag and drop an image into the search bar at Google then crawls its database and provides matches for those images. It all sounds so innocent, right?

But come on, forget identifying that wildflower or national monument, we want to know if this service -- which can also be described as a reverse image search -- can help us find out who Smartdude99 is.

And apparently, it can.

A friend of mine decided on a whim to to drag into Google's image search a photo of someone he'd been corresponding with on an online dating site, and wham -- Google pulled up his prospect's full name and place of work.

He also found that by dragging about 35 anonymous photos from dating sites like and into Google's Image Search field, six came back with hits that revealed the person's identity. In two cases, it brought up Facebook profiles with first and last names; in two other cases the results showed the individuals' work websites, including their full names and place of business. In one case, the image returned an identity match on JDate (thus revealing the man's religious background), and in one case what it revealed was not the person's identity at all, but instead that he was using a press photo of a Bollywood movie star.

All of which is cool if you are the one doing the searching, but what if you aren't?

At this stage, Search by Image is based on computer vision technology, not facial recognition technology, which actually recognizes faces by analyzing facial features, looking for matches in nose shapes, distance between eyes, etc. Instead it's "content-agnostic," meaning that it only pulls up matches when it's the exact same image, even if cropped or resized. (Tags and filenames are irrelevant, so it doesn't matter what the images are labeled.)

This means if you're using the same photo somewhere else on the web, Google will find it -- and with it, all the accompanying information about that person. In other words, Search by Image has made internet stalking dramatically easier. That can be positive, of course -- it might be good, for instance, to know before you go on vacation if the Airbnb user whose place you're renting is a founder of the local S&M club. It's an easy way to check whether check to see if anyone is using your photo in an unauthorized manner (another one of my friends was surprised to see that a few sites were using his headshot without permission). But it's also a handy way for a guy on an online dating site you use to find out your name and other personal information.

It gets creepier: If there's enough data on you out there, Google can pull up who you are even if it's not the exact same photo. Its "Visually Similar" feature can pull up different photos of the same person because, according to a Google spokesperson, more "documentation and activity around an object" leads to more results. For now, it seems like it only works for famous folks like Derek Jeter, or in this disturbing case, Michelle Obama -- but as more and more data and images gets added to the web, the search could eventually identify ordinary users (for example, it identifies Amy Gonzalez, the faux love interest in Catfish). Google also allows you to search by an image plus keyword--so if you have a few data points about the person, like a first or last name, your search becomes even more powerful.

Believe it or not, the service technically doesn't violate any privacy laws. "It's positively spooky," says Ben Edelman, an assistant professor at Harvard Business School who specializes in online privacy issues. "But it's hard to point to a U.S. privacy law that this violates. The data is there, fair and square." Jeffrey P. Cunard, an attorney who works in digital privacy issues at Debevoise & Plimpton, LLP, agrees. "I don't think there are any legal issues here -- privacy laws are violated if you tell the user you're going to do one thing with their information, and then you do something else. That's not happening here -- Google is just finding and matching publicly available information." (If Search by Image did use facial recognition technology, it might be wading into tricky legal territory. "We won't add face recognition unless we have strong privacy protections in place, and we don't have anything to announce," a Google spokesperson told me.)

So how can you prevent yourself from being easily stalked online via your photo?

"Don't use images of yourself when it's not needed," suggests one Silicon Valley tech expert. "Use an avatar or symbolic photo instead." And definitely don't use the same photo of yourself in work and a dating or anonymous setting. This doesn't just include photos of yourself, but your home, kids, even your pets -- given how wide Google's database is now, and how much more powerful its search is with images in the mix (it has indexed 10 billion images to date), connections can be pulled up in an instant.

If you search and find unauthorized images of yourself on the web, you should first contact the webmaster of the site to take it down. You can also use a tool called Me on the Web, a feature of the Google Dashboard that helps you monitor and learn about how to control your identity on the web.

In the meantime, check out your photo, take down unnecessary pics, and scope out your prospective dates (especially before they read this). Bollywood poseurs, be warned.