Facebook's recent effort to improve user privacy controls didn't quite work.

Following Facebook's deployment of improved privacy controls last week, Byron Ng, a computer technician from Vancouver, British Columbia, began testing whether the privacy controls worked.

It turns out they didn't. Ng was able to pull up private pictures of Paris Hilton at the Emmy Awards and of her brother Barron Nicholas, along with other access-restricted pictures, according to The Associated Press.

The AP said it verified Ng's claim by accessing a personal photo that Facebook founder Mark Zuckerberg had posted in 2005.

A spokesperson for Facebook said in an e-mail that the privacy hole was a bug and that it was fixed immediately. "We take privacy very seriously and continue to make enhancements to the site," the spokesperson said.

Facebook and other social networking sites have continued to prosper despite ongoing warnings about the risks of revealing too much information online.

In a blog post over the weekend, Petko D. Petkov, founder of security consulting firm GnuCitizen, calls social networks an "extremely bad idea from a security standpoint." He warns that the proliferation of personal information in social networking profiles enables malicious identity attacks, which he calls "evil twin attacks."

Last week, the Children's Charities' Coalition for Internet Safety, a U.K.-based group, published an open letter asking U.K. government officials to make it illegal for companies and educational institutions to scan social networking profiles for information that might be used to influence hiring or admission decisions.

The group acknowledged that using the Internet to gather publicly available information can be beneficial for companies and educational institutions, but it worried that pursuing such research avenues as a matter of course might disadvantage those who don't participate online. It also expressed concern that unverified information, information taken out of context, or information intended to be private might unduly influence hiring or admissions procedures.

Social networking sites have also weathered repeated criticism for not doing enough to keep sexual predators away from their sites. In October, Facebook, in response to an investigation initiated by New York Attorney General Andrew Cuomo, said it would implement new measures to protect against sexual predators, obscene content, and harassment.