Cyberattackers curious about the contents of users' hard drives will now have a tougher time finding that information, thanks to a new patch that Microsoft issued Tuesday in the latest round of "Patch Tuesday" bug fixes.
This iteration of Patch Tuesday fixes, which Microsoft releases on the second Tuesday of each month, was a relatively small one for the company, said Amol Sarwate, director of vulnerability research at IT research firm Qualys. This edition contains four bulletins covering 42 vulnerabilities.
Microsoft marked one bulletin, covering Internet Explorer, as critical, which means administrators and users should test and apply that bulletin's patches as soon as possible.
The three remaining bulletins, all marked as important, fix potential security problems in ASP.Net, Windows and Lync Server.
The IE bulletin, MS14-052, bundles fixes for 37 vulnerabilities, including one that fixes an active zero-day vulnerability, meaning the bug is already being harnessed by malicious attackers to compromise systems.
The flaw has been known for some time -- the vulnerability was described in detail last year in the CVE 2013-7331 entry of the National Vulnerability Database.
Only recently has Microsoft seen some malicious activity around the bug. It can be exploited to unearth path names, file names and Internet Protocol addresses on a Windows machine. The vulnerability has been used "to find machines without anti-malware or anti-virus support," so attackers can target the machine for further penetration, Sarwate said.
Such information can be particularly damaging for enterprise computers, given that they are all likely to have similar file structures: Understanding the file structure of one machine will give malware writers a good idea of how the others are structured.
Web administrators running Microsoft's ASP.Net should immediately look at MS-14-053, which repairs a bug that could be used for DoS (denial of service) attacks, where the server gets flooded with requests it can't handle and thus can no longer serve its users. Although only marked as important by Microsoft, it should be treated with the highest priority by shops running ASP.Net, Sarwate said.
"It allows a remote unauthenticated attacker to send malformed HTTP or HTTPS requests that could cause a denial of service attack," Sarwate said. "It could take down your server."
The third bulletin, MS14-054, covers a hole in the Windows task scheduler that could allow malware to gain full administrative privileges, in effect granting full control of the machine to the malicious software.
The final bulletin, MS14-055, addresses a vulnerability in Lync Server in which an unauthenticated user can send a malformed SIP (Session Initiation Protocol) packet to the server that would initiate a DoS attack. "It's a pretty important [fix] if you are running a Lync server," Sarwate said.
In addition to Microsoft's patches, administrators should look at a patch Adobe released for its Flash multimedia software. Adobe, which follows Microsoft's "Patch Tuesday" schedule, also plans to release an out-of-band critical patch for Reader next week, after some additional testing is done.
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