Well, it took a bit longer than many security experts expected, but the first big security threat for Windows XP users has arrived. The zero day vulnerability will be quickly patched by Microsoft--for supported platforms at least. That means that this will be the first of many open wounds for Windows XP--known vulnerabilities left exposed because the OS is no longer supported by Microsoft.
Security vendor FireEye notified Microsoft about exploits detected in the wild being used against Internet Explorer. The attack in question is specific to IE 9, 10, and 11, but according to Microsoft the underlying vulnerability exists in all versions of Internet Explorer, as well as all supported versions of the Windows operating system other than Server Core. The attack also seems to rely on having Adobe Flash installed.
Microsoft describes some mitigating factors in its security advisory. For example, most versions of Windows Server run in a restricted mode called Enhanced Security Configuration that guards against this threat. The default configuration for Microsoft Outlook, Outlook Express, and Windows Mail is to open HTML messages in the restricted zone, which disables ActiveX controls and reduces the risk. Microsoft also points out that successful exploitation only allows the attacker to access the system or run code in the context of the current user, so systems where the user has fewer rights and privileges are at less risk.
That's the first part of why Windows XP is actually at greater risk. Windows XP hails from a bygone era where every user was emperor of his own machine. It is common on Windows XP systems for every user to have complete Admin rights on the PC, which means that this attack--and most other malicious attacks out there--will enable the attacker to have carte blanche access to the compromised system.
Many security experts are recommending that businesses and individuals stop using Internet Explorer pending a fix from Microsoft. The flaw is a function of Internet Explorer, so switching to Firefox or Chrome should be enough to protect you from this specific attack, even on Windows XP.
One of the issues when it comes to Windows and Internet Explorer, though, is that the two are often intertwined in ways users may not anticipate or be aware of. At one point in the past Internet Explorer was inexorably woven into the core of the Windows operating system, and many Microsoft applications like the Microsoft Office programs leverage Internet Explorer functionality to render HTML. In other words, just switching browsers may not be enough in all cases.
"The bug is within vgx.dll, which is a library used for handling vector markup language and technically could be used by applications other than just IE," says Andrew Storms, senior director of DevOps for CloudPassage. "In theory, there could be other attack vectors outside of IE, but the likelihood of the attacker making use of those avenues is low."
Wolfgang Kandek, CTO of Qualys, confirms that switching to another browser like Chrome is sufficient to protect Windows XP in this case. "Chrome does not support one of the required formats (VML) so it should not be effected, even if the vulnerable DLL is on the machine."
In fact, regardless of this particular zero day flaw, it's just a good idea to switch to a supported browser like Firefox or Chrome for the duration of your remaining days on Windows XP. There's no point in willingly putting your PC at more risk than you are just by choosing to continue using an unsupported operating system.
"Switching to Chrome or Firefox will enable XP users to remove the relevant attack surface, says Kurt Baumgartner, principal security researcher at Kaspersky Lab. "But they shouldn't be using XP in the first place -- move off of XP people!"
Storms echoes the sentiment. He points out that Windows XP users should be gravely concerned that this issue will never be patched for their OS. Storms stressed that a greater concern than this specific vulnerability is the fact that Windows XP is an outdated operating system and it will soon have many more security problems to contend with.
The best word of advice to XP users is to upgrade.