Zero-day vulnerability

There is no "Super Secure" Browser

Security is a complicated process, leaving many to desire a magic bullet. Unfortunately, there isn’t one. No matter how much security developers build into software, the behavior of the person seated in the chair will always be the weak link. Truth be told, all of the major browsers are safer than the browsing habits of their users. I have advocated safe computing practices for years, especially when it comes to keeping operating systems and applications patched. Sure enough, the best protection against malware is a fully patched system.

Recently, Roger A. Grimes of InfoWorld posted “Browser Security Wars” in his Security Advisor blog. For several months, Grimes tested the five most popular Web browsers: Chrome, Firefox, Internet Explorer, Opera, and Safari. His conclusion is no surprise:

So which one is guaranteed to make your Internet browsing experience perfectly safe?

None, of course. If you have the need for high security on a computer you manage, don’t allow it to surf on the public Web. It’s that simple. Internet browsers are highly complex pieces of software interacting with millions of combinations of highly complex active content and programming code, much of it not so friendly. There is no “super secure” browser.

Not exactly a great revelation; however, there is one surprising discovery: In Grimes’s testing, none of the browsers allowed malware to silently install as long as they were running on fully patched systems. Instead, most of them relied on tricking the user into intentionally running an infected executable:

Almost all the malicious Web sites I came across offered an executable to install, usually in the form of bogus anti-malware software or some sort of content player. In order to be infected, I had to intentionally run the offered executable — not always, but nearly so. There was a smattering of sites that tried to use malformed or mismatched content to trick the third-party software into silently executing code, but it was uncommon; and when my system was fully patched, it never silently succeeded. [Emphasis added]

You’ll find a comprehensive rundown of security features and faults of all the aforementioned browsers in InfoWorld’s special report, “InfoWorld Test Center’s guide to browser security.”

Will They Ever Learn to Patch?

The latest mass infection to hit the Internet is the Win32/Conficker/Downadup Worm, estimated to have already infected between 500,000 and 8.9 million PCs, depending on whose numbers you believe. This is astounding, considering that the worm exploits a vulnerability in Windows that Microsoft Security Bulletin MS08-067 addressed back in October 2008. Microsoft issued an emergency out-of-cycle patch to address the vulnerability. Windows users who have automatic updates enabled would have received the update so the hole is patched. But there are plenty of people and organizations who, for one reason or another, have automatic updates turned off.

Why any individual PC user would put themself at risk by having automatic updates turned off is beyond me. Organizations are another story; they want to test patches before deployment to ensure they don’t break critical applications or disrupt the network. But in this case, the patch should have been applied without question by every sys admin on the planet. Had this happened, the furor surrounding Conficker.A–the original worm–probably would have died down. Instead, enough sys admins left the hole open that a particularly ferocious variant–Conficker.B–surfaced; it’s the one responsible for the current mass infection.

You can read all about Conficker.B and its blended threat in this post at the Microsoft Malware Protection Center, so I won’t burden you with all the gory details about its blended threat here. I will, however, burden you with my informed opinion: Sometimes you have to heed the warnings and go ahead and patch, regardless of what problems that patch could potentially cause. A network taken down by a malware infection is much worse and potentially more costly to repair than a couple of broken apps here and there.

Microsoft Announces Out-of-band Patch for Zero-day Flaw

Microsoft issued today “Microsoft Security Bulletin Advance Notification for December 2008.” The actual security bulletin will be released on December 17, 2008:

Microsoft Security Bulletin Advance Notification for December 2008
Published: December 16, 2008

Microsoft Security Bulletin Advance Notification issued: December 16, 2008
Microsoft Security Bulletins to be issued: December 17, 2008

This is an advance notification of an out-of-band security bulletin that Microsoft is intending to release on December 17, 2008.

This bulletin advance notification will be replaced with the revised December bulletin summary on December 17, 2008. The revised bulletin summary will include the out-of-band security bulletin as well as the security bulletins already released on December 9, 2008.

I don’t have any statistics on how fast they’ve responded to zero-day flaws in the past, but this seems pretty quick to me.

Internet Explorer Targeted by Zero-day Attack

Even though Microsoft released the biggest batch of patches ever on Tuesday–28 flaws affecting Windows, Office, Internet Explorer, Visual Basic Active Controls and Windows Media Player, 23 of them rated “critical”–there’s no fix for a zero-day XML parser vulnerability that surfaced the same day. This was first reported by Robert McMillan of IDG News and was picked up quickly by other media. According to McMillan:

The code exploits a bug in the way IE handles XML (Extensible Markup Language) and works on the browser about “one in three times,” Huang said in an instant message interview. For the attack to work, a victim must first visit a Web site that serves the malicious JavaScript code that takes advantage of the flaw. …

In attacks, the code drops a malicious program on the victim’s PC which then goes to download malicious software from various locations.

According to a blog post by Symantec:

The vulnerability is caused by a function that incorrectly frees a certain region of heap memory so that an attacker is able to control the EAX register with a specially crafted Unicode URL, which includes the magic “0×0A0A” value in it,” Elia Florio, a security researcher at Symantec, wrote….

Symantec released the antivirus signature Bloodhound.Exploit.219 and IPS signature 23241 - HTTP MSIE Malformed XML BO to protect users against this exploit.

I recommend that anyone using Symantec’s antivirus or IPS products, immediately perform an update. Furthermore, Symantec recommends blocking the following hosts which are apparently being used by the exploit to download and install other malware:

• wwwwyyyyy.cn
• sllwrnm5.cn
• baikec.cn
•  oiuytr.net
• laoyang4.cn
• cc4y7.cn

In its security advisory 961051, Microsoft presents the following mitigating factors:

• Protected Mode in Internet Explorer 7 and Internet Explorer 8 in Windows Vista limits the impact of the vulnerability.

•By default, Internet Explorer on Windows Server 2003 and Windows Server 2008 runs in a restricted mode that is known as Enhanced Security Configuration. This mode sets the security level for the Internet zone to High. This is a mitigating factor for Web sites that you have not added to the Internet Explorer Trusted sites zone.

•An attacker who successfully exploited this vulnerability could gain the same user rights as the local user. Users whose accounts are configured to have fewer user rights on the system could be less affected than users who operate with administrative user rights.

•Currently known attacks cannot exploit this issue automatically through e-mail.

Nevertheless, users should avoid using Internet Explorer and should instead use Firefox with the NoScript extension installed until Microsoft issues a patch. We may see an out-of-cycle patch on this one according to the security advisory:

We are actively investigating the vulnerability these attacks attempt to exploit. We will continue to monitor the threat environment and update this advisory if this situation changes. On completion of this investigation, Microsoft will take the appropriate action to protect our customers, which may include providing a solution through a service pack, our monthly security update release process, or an out-of-cycle security update, depending on customer needs.

Well, since I’m forced to use IE for certain applications in my job, this customer needs a patch as quickly as possible.

Opera Zero-day Vulnerability

Just as Opera completed patches for critical vulnerabilities in its browser, researchers discovered another remote code execution bug. In its recent article, “Opera scrambles to quash zero-day bug in freshly-patched browser,”
The Register reports:

Among the bugs squashed in Opera 9.61 was a stored cross site scripting (XSS) vulnerability that allowed attackers to view victims’ browsing history. That attack is no longer possible, but now researchers have discovered an even more serious exploit that’s based on the same weakness.

Until Opera releases version 9.62, which should be “very, very soon” according to Opera spokesman Thomas Ford, your best bet is to disable iFrames and turn off scripting. Open opera:config and select Extensions|iFrames. Change the setting from “1″ to “0.” Similarly, change Extensions|Scripting from “1″ to “0.”

Bear in mind that the above temporary workaround is going to break a lot of sites that use scripting. It would be simpler if Opera had some way to designate “trusted sites” (or a plug-in like NoScript), but I’m not aware of any way to do this. Hit the comments and let me know if there’s a better workaround (I haven’t used Opera since my conversion to Firefox four years ago).