Microsoft's claims that Internet Explorer 9 (IE9) blocks attacks just don't add up, a security researcher charged Friday.
"They're presenting only half of the equation," said Chet Wisniewski, a security researcher at Sophos. "They put lots of numbers to make it seem all 'sciencey,' but they raise more questions than they answer. So really, where's the beef?"
Wisniewski was reacting to a blog post by Jeb Haber, the programme manager lead for Microsoft 's SmartScreen technology. In this post, Haber cited a wide range of statistics to show that IE9, which includes a new feature dubbed SmartScreen Application Reputation, has blocked a significant number of attempted malicious downloads from reaching PCs running Vista or Windows 7.
Among Haber's key points: Microsoft's data showed that one in every 14 downloads by Windows users is malicious, and thus blocked by IE9.
Microsoft also argued that IE9's Application Reputation, or "App Rep," stymied socially engineered attacks, the kind that rely on duping users into downloading and installing a dangerous file containing code that compromises a computer and infects it with malware.
"Microsoft is comparing apples to... nothing," said Wisniewski. Because IE9's unable to block exploits of such software as Adobe Reader and Flash, Apple's iTunes or Oracle's Java, Microsoft's data doesn't show the real picture.
"Where are the numbers of exploits?" Wisniewski asked, referring to the attacks, often conducted not through downloads but by drive-by hacks leveraging vulnerabilities in Microsoft's own software or popular third party programs.
The result is a partial picture, one that Microsoft presented as public relations move, said Wisniewski. "They're not comparing their numbers with actual exploits, so I feel like they're lying to me," he said. "No way do I ever get near a factual argument."
Wisniewski also pointed out flaws in IE9's download blocking, using Microsoft's own statistics to back up his case.
Haber said that 90% of all downloads do not trigger a warning by IE9, but of the 1 in 10 downloads that do display an alert, the "false positive" rate, meaning that the warning was incorrectly flagging a legitimate file, was between 30% and 75%.
"If that's true, will you continue to pay attention to the warning when it really matters?" Wisniewski asked. "People may get sick of it, just like they did with [User Account Control] warning in Vista."
IE9's App Rep uses a file's hash, which identifies the file contents, and its digital certificate to determine whether it's a known application with an established reputation. If the App Rep algorithm ranks the file as unknown, perhaps because the hash value hasn't been seen before, IE9 throws up a warning when users try to run or save the file.
Wisniewski noted problems with that approach.
"The problem with code signing is that we regularly see it abused," Wisniewski said, using the Stuxnet worm as an example. One variant of Stuxnet, the worm that experts have concluded was created to wreak havoc on Iran's nuclear programme, used a pair of stolen certificates to masquerade as legitimate software.
"One of the things that Zeus does is grab all the digital signatures on a [compromised] computer," Wisniewski added, talking about the pervasive crimeware kit responsible for a large percentage of financially motivated hacks.
Legitimate software that hasn't yet been "approved" by Microsoft could also confuse users into either rejecting the download, bad for that product's developer, or worse teach IE9 users to ignore the warnings altogether.
"I love the idea of reputation-based blocking moving forward," acknowledged Wisniewski, who tipped his hat to Microsoft and IE9 for "trying to get ahead of the curve" with App Rep. "We're doing about all we can do in the reaction side.
But in his eyes, Microsoft's missed an opportunity by touting numbers that told only half the story. "They made this PR move, showing us half the picture," he said. "They missed the mark."