Morto RDP Patch Is Critical Feature Of Microsoft’s Patch Tuesday Issue

Microsoft’s March Patch Tuesday might be light on actual bulletins – there are only six – but security researchers are nonetheless advising companies to fix the most critical one immediately.

That critical bulletin, MS12-020 (Windows) addresses an issue in Remote Desktop Protocol (RDP). While Microsoft insisted in a posting on the Microsoft Security Response Center blog that “we know of no active exploitation in the wild”, it also advised that “customers examine and prepare to apply this bulletin as soon as possible”.

Shut out remote code attackers

As it stands, the vulnerability allows an attacker to achieve remote-code execution; Microsoft is offering a one-click, no-reboot fix-it “that enables Network-Level Authentication, an effective mitigation for this issue”.

Of the five other bulletins, two are rated “important” and relate to Expression Design (MS12-022) and Visual Studio (MS12-018). Two other important ones apply to different configurations of Windows and Windows Server, and focus on Kernel (MS12-018) and Domain Name System (DNS) (MS12-017). The last, rated “moderate”, deals with DirectWrite (MS12-019).

But outside analysts hammered home Microsoft’s point about the urgency in patching the RDP vulnerability.

“Last fall we saw the RDP worm Morto attacking publicly exposed Remote Desktop services across businesses of all sizes with brute-force password guessing,” Kurt Baumgartner, senior security researcher for Kaspersky Lab, wrote on Securelist. “The Morto worm incident brought attention to poorly secured RDP services. Accordingly, this Remote Desktop vulnerability must be patched immediately.”

Unfortunately, he added, most companies fail to sufficiently secure their RDP services. “It seems to me that every time a small and medium-sized organisation runs a network, the employees or members expect remote access,” he wrote. “In turn, this Remote Desktop service is frequently exposed to public networks with lazy, no-VPN or restricted communications at these sized organisations.”

Instead, he advised, “RDP best practices should be followed requiring strong authentication credentials and compartmentalised, restricted network access.”

Other analysts agreed with that assessment. “This patch should be your highest priority if you use RDP,” wrote Paul Henry, security and forensic analyst at Lumension, in reference to MS12-020.

Organisations should disable RDP when not needed, added Marcus Carey, security researcher at Rapid7. “Organisations should also apply appropriate ingress firewall rules where they can,” he wrote. “Organisations should be ready to test and deploy the patch as soon as possible. RDP is not enabled by default, but many times it is turned on for administration tasks and just left enabled.”