Companies have several options for defending against a recently discovered zero-day vulnerability in Internet Explorer and experts say businesses should get started immediately.
Over the weekend, security vendor FireEye found an exploit aimed at defense and financial services companies using IE9 through IE11. The exploit was found in a "very popular U.S. website," which has removed the malicious code, Dan Caselden, senior vulnerability researcher for FireEye, said.
Microsoft released an advisory Saturday, the same day FireEye announced the discovery, and provided some guidance on how to handle the vulnerability that affects IE 6 through IE11. The company has not said when it would release a fix, which could come before or on the day Microsoft releases its regular security updates on the second Tuesday of each month.
Until a patch is available, companies' options range from disabling Adobe Flash Player and downloading a Microsoft toolkit to segmenting the corporate network, experts said Monday.
Organizations still using Windows XP should recognize they are at particular risk, because Microsoft stopped supporting the operating system April 8. XP accounts for roughly a quarter of all online PCs worldwide, according to the latest numbers from Net MarketShare.
For now, cybercriminals can develop fresh exploits only by reverse engineering the original. Other exploits are not expected to appear en masse until after Microsoft releases a patch, which hackers are sure to tear apart to find the vulnerability, dubbed CVE-2014-1776.
Prudent companies will start preparing now for the possibility of an attack. Until Microsoft issues a patch, companies could run IE under the default Enhanced Security Configuration, which would block the exploit from a malicious website, assuming it is not on a white list of trusted sites.
However, experts acknowledge that the reason companies do not use the default configuration is because it sometimes breaks sites and business applications running in IE.
Therefore, the better option is to deploy the latest version of Microsoft's Enhanced Mitigation Experience Toolkit. The utility contains security mitigation technologies that security pros can use in defending against attacks, even those that target Windows XP systems.
"That's the best control to go to in protecting yourself against this type of vulnerability," Ross Barrett, senior manager of security engineering at risk management company Rapid7, said of EMET.
The current exploit can also be mitigated by disabling Adobe Flash Player, which is the vehicle used in exploiting the IE flaw. FireEye has posted the technical details of how this is done in its blog.
The U.S. Computer Emergency Readiness Team (US-CERT) has advised companies to use an alternative browser until a fix is available. However, for many companies that is not an option, since business applications often depend on IE.
The attackers discovered by FireEye take advantage of the fact that most people use PCs in administrator mode, which gives full access to the system. Once breaking into the system of such a user, the hackers proceed to move within a network looking for way to escalate the privileges to gain access to more data and systems.
As a best practice, companies should only provide administrative access to people who have a need for it in doing their job. Others, should be cutoff from functionality in a PC they don't need.
Some experts recommend segmenting the corporate network to confine people to specific areas, which would also contain the mischief of hackers.
"Any organization that has properly segmented their network will be at low risk to sensitive data being accessed as a result of a breach related to this attack," Brandon Hoffman, vice president of cybersecurity at RedSeal Networks, said in an emailed statement.
However, other experts say employees often find ways around those restrictions, which tend to poke holes in defenses that cybercriminals could exploit.
"You're just going to spend so much energy and time to implement that and enforce that and you're not paying attention to things that matter," Barrett said.