For this month's "Patch Tuesday" round of bug fixes, Microsoft has focused on correcting multiple vulnerabilities in Internet Explorer (IE), including one that is already being used in targeted attacks.
Overall, Microsoft issued five bulletins, covering 23 vulnerabilities. Two of the bulletins, covering IE and Windows, are marked critical, which means administrators should test and apply them as soon as possible. The remaining bulletins, marked important, cover Windows and the Silverlight multimedia plug-in.
Administrators should look first at MS-1402, covering 18 patches for IE, including one patch for a publicly disclosed zero-day vulnerability.
The public vulnerability first surfaced during last month's Patch Tuesday, noted Wolfgang Kandek, chief technology officer of IT security firm Qualys.
The public exploit that used this vulnerability worked in conjunction with a flaw in Adobe Flash. "Most of the time a single vulnerability will not get you that far," Kandek said, of today's approaches to compromising systems by chaining together multiple vulnerabilities. A browser vulnerability can get you into a computer, but you'd need another object to give you a specific memory location, in this case Flash.
The patches in MS-1402 cover all versions of IE, though the zero day vulnerability affected versions 9 and 10, and the known attacks using this vulnerability appeared only for IE 10.
Another interesting aspect of this zero day exploitation is that it first appeared on the Web site for the Veterans of Foreign Wars (VFW), leading some to suspect it was part of an attack from another nation, rather than just from profit-minded cybercriminals, who tend to target sites with more traffic.
"In the past, this was called a waterhole attack. You infect a website that you think your targets will go to," Kandek said. Since most of the users of the Veterans Affairs site are military or ex-military personnel, security experts suspect this group was targeted deliberately.
Microsoft is also urging administrators to take a close look at the other critical bulletin, MS-1403. Applying these patches can have "a long term impact in improving your systems' security," advised Dustin Childs, Microsoft Trustworthy Computing group manager, in a statement.
Microsoft stated that while this vulnerability is just as severe as the ones for IE, it would take a malicious user more time to understand it and write code that would exploit its weakness. "Nevertheless you should fix it, though the urgency would be lower than the browser fix," Kandek advised.
All of this month's bulletins affect Windows XP, for which Microsoft will be ending support next month. Microsoft, along with most security organizations, has been urging XP users to upgrade,with somewhat limited results. After April, Microsoft will no longer fix newly discovered XP security holes.
As a result, Windows XP will become much less secure in the coming months, Kandek warned. Given the size of the Windows code base, many of the patches that Microsoft issues each month cover vulnerabilities found in all versions of Windows, at least back to XP. After April, attackers can examine these patches to pinpoint where vulnerabilities may be, and seek them in the no-longer supported Windows XP.
"Half of the work has already been done for them," Kandek said.
Qualys tracks the percentage of its enterprise users that still deploy XP. In February that number has shrunk to about 14 percent, two percentage points lower than the month prior.
Joab Jackson covers enterprise software and general technology breaking news for The IDG News Service. Follow Joab on Twitter at @Joab_Jackson. Joab's e-mail address is Joab_Jackson@idg.com