As promised, Microsoft today issued an emergency patch for the critical Windows shortcut bug attackers have been exploiting for several weeks.
Also as pledged, Microsoft did not deliver a fix for users running Windows XP Service Pack 2 (SP2) or Windows 2000, which were retired from support three weeks ago.
There was little in Monday's accompanying bulletin that wasn't already known, noted Andrew Storms, director of security operations at nCircle Security.
"This was almost entirely public at this point," said Storms. "The only question I had was whether Microsoft would try and release a patch for unsupported operating systems."
Storms' reference was to XP SP2 and Windows 2000. "There's a ton of people still running SP2, and it just went end-of-life," Storms argued. "And SCADA systems typically run on older versions of the OS. I thought Microsoft might be strong-armed by SCADA vendors into releasing a fix for SP2."
But Microsoft stuck to its long-standing policy and did not provide patches for machines running Windows XP SP2, Windows 2000 or any other off-support version.
The vulnerability addressed today was first described in mid-June by VirusBlokAda, a little-known security firm based in Belarus, but attracted widespread attention only after security blogger Brian Krebs reported on it July 15. A day later, Microsoft admitted that attackers were already exploiting the flaw using the "Stuxnet" worm, which targets Windows PCs that manage large-scale industrial-control systems in manufacturing and utility firms.
Those control systems are often dubbed SCADA, for "supervisory control and data acquisition."
The flaw was in how Windows parsed shortcut files, the small files displayed by icons on the desktop, on the toolbar and in the Start menu that launch applications and documents when clicked. By crafting malicious shortcuts, hackers could automatically execute malware whenever a user viewed the shortcut or the contents of a folder containing the malevolent shortcut.
Exploit code went public last month, and Microsoft and others have spotted several attack campaigns based on the bug. When the company announced last Friday that it would patch the shortcut bug today, it also said that it had seen the virulent "Sality" malware family using the shortcut exploit.