Three Google Inc researchers have uncovered a security bug in widely used web encryption technology that they say could allow hackers to take over accounts for email, banking and other services in what they have dubbed a "Poodle" attack.
The discovery of Poodle, which stands for Padding Oracle On Downloaded Legacy Encryption, prompted makers of web browsers and server software to advise users on Tuesday to disable use of the source of the security bug: an 18-year old encryption standard known as SSL 3.0.
It was the third time this year that researchers have uncovered a vulnerability in widely used web technology, following April's Heartbleed bug in OpenSSL and last month's Shellshock bug in a piece of Unix software known as Bash.
Security experts said that hackers could steal browser "cookies" in Poodle attacks, potentially taking control of email, banking and social networking accounts. Even so, experts said the threat was not as serious as the two prior bugs.
"If Shellshock and Heartbleed were Threat Level 10, then Poodle is more like a 5 or a 6," said Tal Klein, vice president with cloud security firm Adallom.
The threat was disclosed in a research paper published on the website of the OpenSSL Project, which develops the most widely used type of SSL encryption software.
Rumors of a bug in SSL software had been circulating in recent days, prompting some security professionals to prepare for a major new threat this week.
Attack using Poodle would be 'quite complicated'
Ivan Ristic, director of application security research with Qualys, said Poodle was not as serious as the previous threats because the attack was "quite complicated," requiring hackers to have privileged access to networks.
Jeff Moss, a cyber adviser to the U.S. Department of Homeland Security, said attackers would need to launch a "man-in-the-middle" attack, placing themselves between victims and websites using approaches such as creating rogue WiFi "hotspots" in Internet cafes.
Google suggested a technical workaround to secure web servers, but added on its blog that it hopes to eventually remove support for SSL 3.0 from all client software.
Mozilla plans to disable SSL 3.0 by default in the next version of its Firefox browser, to be released on Nov. 25.
"SSL version 3.0 is no longer secure," Mozilla said on its blog. "Browsers and websites need to turn off SSLv3 and use more modern security protocols as soon as possible."
Microsoft Corp issued an advisory suggesting that customers disable SSL 3.0 on Windows for servers and PCs.
Representatives with Apple Inc could not be reached. An Oracle Corp spokeswoman had no immediate comment.
Matthew Green, an assistant research professor of computer science at Johns Hopkins University said that disabling SSL 3.0 can be difficult for some computer users.
"It's not going to take out the infrastructure of the internet. But it's going to be a hassle to fix," Green said.