Rogue programs try their best to register at Web sites and then wreak havoc, but a clever puzzle often bars them from entry: a set of distorted, squiggly letters and numbers that people can decipher and type correctly for admission, but that machines still can’t.
Well, at least for the moment.
Now, to stay one jump ahead of fraudsters and their automated programs, researchers are devising more versions of the puzzles, called captchas, to help sites block abuse that includes spam e- mail, illegal postings and skewed online voting.
Researchers at Google are testing a new captcha that requires people to turn upright randomly rotated images, like that of a parrot perched temporarily upside-down on a leafy branch. The task is a breeze for people — using a cell phone touchscreen, for example, to flip the image — but hard for machines.
The new puzzles could be built around a site’s theme — for instance, cartoons at a Disney site, or objects for sale at eBay, said Rich Gossweiler, a senior research scientist at Google who led the team that developed the system. It lends itself to rapid implementation, he said, and has an almost limitless supply of images. “Our technique expands the vocabulary of captchas” beyond obfuscated characters, he said. “And it might make the process less of a chore. It’s fun to solve a puzzle.”
The program rejects images like those for human faces that computers have already learned to recognize. “We first remove all those images that computers can turn upright, and then the ones that humans have trouble with,” Dr. Gossweiler said.
People may have trouble orienting abstract art, but they can quickly distinguish a parrot’s image, for example, even if it is shown amid objects like leaves. “We can see it needs to be upright,” he said, “but it’s more difficult…