Microsoft patches Remote Desktop Protocol hole but danger remains

Exploits likely to appear within days, maybe even worms, say experts

At first glance Microsoft patch MS12-020 looks routine. A security vulnerability in the Remote Desktop Protocol (RDP) was closed. End of story. But some Australian security researchers think it's far more serious.

They're even building a tool to tell you whether you're at risk.

RDP, also known as Terminal Services (TS), is widely deployed in businesses large and small to provide a graphic interface to a remote computer.

Even though RDP is turned off by default, figures published by Hacklabs show that 98 per cent of its customers run RDP internally and 30 per cent have had RDP on an Internet-facing Windows host.

Often RDP provides the access to a company's cloud servers, or allows external IT contractors to manage internal servers and networks.

The vulnerability, assigned CVE number CVE-2012-0002, allows a remote attacker to gain control of a machine by sending it a sequence of specially-crafted RDP packets.

The vulnerability exists in all currently-supported versions of Windows, i.e. back to Windows XP and Windows Server 2003.

"Anyone who can access the vulnerable service and has the exploit will be able to get a system-level privilege on the targeted machine," Casey Ellis of Tall Poppy Group told CSO Online.

A vulnerability in a widely-deployed internet-facing service that exists in every version of Windows is particularly attractive to criminals.

Even though patch MS12-020 was released Tuesday to fix the problem, many systems will remain unpatched and vulnerable for weeks or even months. And because Microsoft has released the patch, the bad guys can now start reverse engineering it to develop an exploit.

"I would think that we'll see this getting exploited within a week," Ellis said.

Hacklabs proprietor Chris Gatford agrees with Ellis' assessment.

"I believe on past experience that exploit code is probably 10 days off, and highly likely in 30 days," Gatford said.

Ellis and fellow security consultant Serg Belokamen, who works for a major consulting firm, are creating a software tool called RDPCheck to help identify vulnerable systems.

Currently, their website is a holding page where people can register their interest. The working tool is expected to be available in the next few days.

"Because of the number of instances of this protocol sitting out on the web there are, and the type of vulnerability it is, I wouldn't be surprised if it turns into a worm at some point," said Ellis.

With RDP being used internally by so many organisations as well as externally, it could end up being something like Blaster or Sasser worms from 2003.

"When that happens, the profile of the vulnerability, and the number of people that are going to be out there looking for help, it's going to go through the roof very quickly," Ellis said.

Contact Stilgherrian at Stil@stilgherrian.com or follow him on Twitter at @stilgherrian

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