A recent string of high-profile ActiveX vulnerabilities caused the U.S. Computer Emergency Readiness Team (US-CERT) to advise users to disable the ubiquitous Microsoft browser plug-in technology altogether. The vectors for these recent exploits include a third-party image uploading tool used on both the Facebook and MySpace social networking sites, and flaws found in Yahoo's Music Jukebox, Real Networks' RealPlayer, and Apple's QuickTime.
Security experts contend that there's no end in sight for attacks on the plug-in architecture.
One reason is that there are plenty of security holes in ActiveX to be exploited. But another reason is not Microsoft's fault, they say: any technology used so widely will attract hacker attacks. "There's simply a lot of software out there using ActiveX that's either preloaded or embedded that users don't even realize is there, and that's why it was necessary to make the advisory," the US-CERT spokesman said.
Although features added in Microsoft's newest Web browser, Internet Explorer 7, may help reduce the problem down the road and push attackers to move on to new targets, ActiveX will remain among the leading programs assaulted by opportunistic cyber-criminals, at least for the foreseeable future, several researchers say. After all, they say, Internet Explorer's status as the most used Web browser makes it an attractive target, just as the Windows operating system has been subject to constant attack for the past decade due to its huge market share. "When hackers spend time trying to find vulnerabilities to exploit, they want to make sure that they can affect the highest number of people," said Will Dormann, a vulnerability analyst at the Carnegie Mellon Software Engineering Institute CERT.
A juicy target that's easier to exploit
When you ask researchers which ActiveX exploits make them curl their toes in reaction, the answers don't tend to focus on specific sets of attacks but instead on the sheer volume and variety of the threats, and the vulnerabilities that allow for them.
Some of the most prominent examples of ActiveX exploits include malware attacks aimed at Microsoft's Data Access Component (MDAC) software, which was pummeled for years by a broad range of attacks, and problems with the HTML Help ActiveX control module in Internet Explorer that opened it to numerous types of attacks, most notably the Phel Trojan virus.
These well-known examples are just the tip of the iceberg for the vulnerabilities that ActiveX exposes users to. One reason is that as Microsoft fixes vulnerabilities in Windows, hackers are moving to easier targets, such as ActiveX, said Randy Abrams, director of technical education at ESET, a maker of anti-malware software. "Applications and plug-ins like ActiveX are the new low-hanging fruit so that's what's being attacked," he said.
Abrams believes that ActiveX introduces unnecessary risk in many cases, because it is typically used for nonessential purposes. "The truth is that the ActiveX problem is also based on an irrational love of fashion; it's all about adding functionality to sites and applications to make them look cool, but in actuality it's completely unnecessary," he said. "If it wasn't for this need to make things look fashionable there would be much less risk." But Abrams doesn't expect developers to throttle back ActiveX use despite its security risks: "The cat is out of the bag, and sites now compete to look visually impressive and offer better functionality."
Many developers of ActiveX-based applications do a poor job of ensuring security, notes Craig Schmugar, a threat researcher at McAfee's Avert Lab. And that threat grows as the number of ActiveX applications grows. "You can improve developer education, but hackers are likely to keep attacking the soft targets," he said.
It's also become easier for hackers to find ActiveX's flaws, thanks to the broad availability of fuzzing tools. "The publicly available fuzz testing tools for ActiveX make it relatively simple to find new vulnerabilities and controls to go after, so people are able to research how exploitable certain applications may be before writing their attacks," said Carnegie Mellon's Dormann. "People are finding new holes all the time and posting them to public mailing lists," he added.
"One of the most telling things to look at with ActiveX is that security researchers delving into these problems don't get a lot of respect within the vulnerability research community itself," Schmugar noted. "That's mostly because with the sheer number of holes, and all the available fuzzing tools, people look at it like shooting fish in a barrel."
IE7 improvements should help over time
Microsoft is well aware that ActiveX is both a big target for hackers and one that they can successfully attack. So the company has re-architected its Internet Explorer Web browser in version 7 to limit the scope of well-known attacks methods. Researchers say that the work should eventually produce dividends.
For example, the original implementation of ActiveX in IE6 and previous versions exposed binaries to any page visited by users. By contrast, IE7 provides far less access to sites and applications, preventing malware authors from activating code that would let them hack the browser.
Microsoft has configured IE7's defaults so that only "safe" ActiveX controls (as determined by Microsoft) can be accessed, and it has enhanced separation of controls to prevent exploits from running roughshod across the entire Internet Explorer application as they often did in the past, researchers said. "IE7's protected mode definitely helps, even if the root cause in the form of ActiveX vulnerabilities is still present, and in the long run it will play a role in convincing attackers to move elsewhere, but with Vista and IE7 in relatively few hands this won't happen soon," said McAfee's Schmugar. Improvements made in the Windows Vista operating system should also help reduce the impact of traditional ActiveX attack techniques, he noted.
However, most people use neither Vista nor IE7, so these improvements aren't widely deployed. The majority of users run IE6 on Windows XP, both of whose ActiveX components remain largely unchanged and thus at high risk.
Dumping ActiveX is not the long-term solution
"The issue goes beyond ActiveX. Any plug-in architecture that has a lot of users will suffer from these same issues; anything where you have third party developers writing code that runs inside the browser," said Max Caceres, director of research and development at applications security firm Matasano Security. "As long as developers are building things without putting security at the top of their list of objectives, we'll have these problems, regardless of the plug-in architecture."