Search engines such as Google are increasingly being used by hackers against Web applications that hold sensitive data, according to a security expert.
Even with rising awareness about data security, it takes all of a few seconds to pluck Social Security numbers from Web sites using targeted search terms, said Amichai Shulman, founder and CTO for database- and application-security company Imperva.
The fact that Social Security numbers are even on the Web is a human error; the information should never be published in the first place. But hackers are using Google in more sophisticated ways to automate attacks against Web sites, Shulman said.
Shulman said Imperva recently discovered a way to execute a SQL injection attack that comes from an IP address that belongs to Google.
In a SQL injection attack, a malicious instruction is entered on a Web-based form and answered by a Web application. It often can yield sensitive information from a back-end database or be used to plant malicious code on the Web page.
Shulman declined to give details on how the attack works during his presentation at the RSA Conference on Monday, but said it involves Google's advertising system. Google has been notified, he said.
Manipulating Google is particularly useful since it offers anonymity for a hacker plus an automated attack engine, Shulman said.
Tools such as Goolag and Gooscan can execute broad searches across the Web for specific vulnerabilities and return lists of Web sites that have those problems.
"This is no more a script kiddy game -- this is a business," Shulman said. "This is a very powerful hacking capability."
Another attack method is so-called Google worms, which use the search engine to find specific vulnerabilities. With the inclusion of additional code, the vulnerability can be exploited, Shulman said.
"In 2004, this was science fiction," Shulman said. "In 2008, this is a painful reality."
Google and other search engines are taking steps to stop the abuse. For example, Google has stopped certain kinds of searches that could yield a trove of Social Security numbers in a single swoop. It also puts limits on the number of search requests sent per minute, which can slow down mass searches for vulnerable Web sites.
In reality, it just forces hackers to be a bit more patient. Putting limits on search also hurts security professionals who want to do automated daily searches of their Web sites for problems, Shulman said.
Shulman said he's seen another kind of attack called "site masking," which causes a legitimate Web site to simply disappear from search results.
Google's search engine penalizes sites that have duplicate content and will drop one from its index. Hackers can take advantage of this by creating a Web site that has a link to a competitor's Web page but is filtered through a proxy server.
Google indexes the content under the proxy's domain. If this is done enough times with more proxy servers, Google will consider the targeted Web page a duplicate and drop it from its index.
"This is quite a business hassle," Shulman said.
One way Web site administrators can defend against this is barring their Web site from being indexed by anything other than the legitimate IP address of a search engine, Shulman said.