(USA TODAY) -- Tara Palardy wants you to know the dog you're approaching might bite your hand off.

Palardy, a Canadian dog trainer from Innisfail, Alberta, founded the Yellow Dog Project in an attempt to raise awareness that not all dogs are social. In just over six months, her campaign has attracted more than 12,000 followers from around the world.

The concept is simple: If your dog doesn't want to be approached, put a yellow ribbon on his collar. The ribbon works as a signal to others to ask before coming near.

It's part of a growing movement to urge people to use caution when approaching dogs. Palardy got the idea from a website launched in Sweden. Since branding her own project, people around the world have started tying bows.

Palardy loved the Swedish group's idea but says she didn't believe the group was doing all it could to spread the message. Palardy acknowledges the movement can only work if people know about it, so to promote her movement, she created a logo and started a Facebook group for the Yellow Dog Project.

Not all dogs who wear the ribbon are aggressive. Many just need space after a surgery, are old or don't like being approached too quickly.

Toby, a dachshund, is scared of big dogs. The phobia makes it tough for his owner, Alice Thurston, a retired federal employee who lives in Washington D.C. When Thurston came across a link to the Yellow Dog Project on Facebook, she decided it was worth a try.

"I just get so tired of having to say, 'You know, my dog is not friendly,' and to have to go out of my way to avoid other dogs," Thurston says. "I'm embarrassed by it."

Jessica Dolce, a professional dog walker from Portland, Maine, walks up to 50 dogs a week. At some point every, dog she walks has needed some space. However, explaining that to people has created awkward situations. The sheer volume of walks she takes means she spends a lot of time trying to politely tell people to back off.

In 2011, Dolce coined the phrase Dogs In Need of Space (DINOS) to help promote the idea that not all dogs want to be approached when they're out.

For Kristel Smart, a writer from South Burlington, Vt., DINOS is especially important. Smart suffers from post-traumatic stress disorder and needs her service dog, Murphy, to keep her calm in public.

She recalls how during a walk in her neighborhood, an off-leash dog came running over and, despite Smart's protests to call him away, the owner kept hollering "He's friendly!" The dog wasn't.

Murphy was attacked, and it took him two years to return to a semi-normal state around other dogs. Murphy became a DINOS during his post-attack therapy. Anytime an unknown dog or person came over, he became panicked and his training was set back months.

"My very well-behaved, well-socialized dog became profoundly leash reactive," Smart says. "It affected me, too, and my ability to do anything, because I depend on my dog for my life."

Despite support from people who have DINOS and a growing online presence, the Yellow Dog Project is struggling to spread awareness. Most people don't understand the significance of the yellow ribbon.

Claudia Kawczynska, editor in chief and co-founder of The Bark magazine, likes the idea of an indicator for dogs who shouldn't be approached but thinks that in larger communities, it will have a hard time catching on.

"It's expecting a lot out of people," Kawczynska says. "Most dog people are very outgoing people because they love dogs and love their dogs to love other dogs."