Spyware Barely Touches Firefox

"We can't say whether Firefox is a safer browser or not," said Henry Levy, one of the two University of Washington professors who, along with a pair of graduate students, created Web crawlers to scour the Internet for spyware in several 2005 forays. "But we can say that users will have a safer experience [surfing] with Firefox."

In May and October, Levy and colleague Steven Gribble sent their crawlers to 45,000 Web sites, cataloged the executable files found, and tested malicious sites' effectiveness by exposing unpatched versions of Internet Explorer and Firefox to "drive-by downloads." That's the term for the hacker practice of using browser vulnerabilities to install software, sometimes surreptitiously, sometimes not.

"We can't say IE is any less safe," explained Levy, "because we choose to use an unpatched version [of each browser.] We were trying to understand the number of [spyware] threats, so if we used unpatched browsers then we would see more threats."

Levy and Gribble, along with graduate students Alexander Moshchuk and Tanya Bragin, set up IE in two configurations -- one where it behaved as if the user had given permission for all downloads, the other as if the user refused all download permission -- to track the number of successful spyware installations.

During Levy's and Gribble's most recent crawl of October 2005, 1.6 percent of the domains infected the first IE configuration, the one mimicking a user blithely clicking 'Yes;' about a third as many domains (0.6 percent) did drive-by downloads by planting spyware even when the user rejected the installations.

"These numbers may not sound like much," said Gribble, "but consider the number of domains on the Web."

"You definitely want to have all the patches [installed] for Internet Explorer," added Levy.

In the same kind of configurations, Firefox survived relatively unscathed. Only .09 percent of domains infected the Mozilla Corp. browser when it was set, like IE, to act as if the user clicked through security dialogs; no domain managed to infect the Firefox-equipped PC in a drive-by download attack. Compare those figures, and it seems that IE users who haven't patched their browser are 21 times more likely to have a spyware attack executed -- if not necessarily succeed -- against their machine.

Most of the exploits that leveraged IE vulnerabilities to plant spyware were based on ActiveX and JavaScript, said Gribble. Those two technologies have taken the blame for many of IE problems. In fact, Firefox boosters often point to their browser's lack of support for ActiveX as a big reason why its security claims are legit.

Levy and Gribble didn't set out to verify that, but they did note that the few successful spyware attacks on Firefox were made by Java applets; all, however, required the user's consent to succeed.

Microsoft's made a point to stress that Internet Explorer 7, which just went into open beta for Windows XP, tightens up ActiveX controls by disabling nearly all those already installed. IE 7 then alerts the user and requires consent before it will run an in-place control.

Good thing, because one of the research's most startling conclusions was the number of spyware-infected sites. One out of every 20 executable files on Web sites is spyware, and 1 in 25 domains contain at least one piece of spyware waiting for victims.

"If these numbers are even close to representative for Web sites frequented by users," the paper concluded, "it is not surprising that spyware continues to be of major concern."

The moral, said Levy, is: "If you browse, you're eventually going to get hit with a spyware attack."