Dark Reading is part of the Informa Tech Division of Informa PLC

This site is operated by a business or businesses owned by Informa PLC and all copyright resides with them.Informa PLC's registered office is 5 Howick Place, London SW1P 1WG. Registered in England and Wales. Number 8860726.


03:57 PM
Connect Directly

Microsoft Flaw Demonstrates Dangers Of Remote Desktop Access

Fear is that attackers will soon come up with exploits for targeted attacks, worms

Microsoft's Patch Tuesday warning of possible attacks emerging quickly for a vulnerability in its Remote Desktop Protocol (RDP) is a chilling reminder of the potential dangers of desktop remote-access tools commonly used by IT departments to handle from afar help-desk issues and by administrators to manage virtualized machines.

The sole "critical" vulnerability among the updates in Microsoft's batch of patches yesterday was for a flaw in Microsoft's implementation of RDP, which gives one user remote access to another's desktop. Microsoft strongly urged users to patch this one (CVE-2012-002 in MS12-020) as soon as possible, or to apply the FixIt temporary fix that was also issued among the updates. Other security organizations, such as SANS, and vendors echoed Microsoft's warning that this particular patch should be a priority this month.

"Although Remote Desktop Protocol, RDP, is not enabled on the default configuration for any version of Windows, Microsoft strongly recommends that all customers prioritize the MS12-020 security update this month, in order to ensure that systems are protected," a Microsoft spokesperson said. Microsoft says an attacker could reverse-engineer its new patch for the RDP bug in relatively short order, which raises the potential for exploits to be written for a targeted attack or for automatic-propagation worms that would let attacks quickly take over systems within corporate networks for botnets or other purposes.

That's a scary scenario, security experts say. "We saw this two months ago with Symantec's pcAnywhere" remote-desktop tool code leak," says Wolfgang Kandek, CTO at Qualys. "All of these remote-access tools are great for productivity, but when you set them up and look at who connects and how you can restrict that," it's just username and password, which is weak, Kandek says.

Remote-desktop access tools are popular among organizations with branch offices and users who work at home: Rather than the old days where the IT guy flew to the branch office to physically work on the user's machine, the tools allow IT and security teams to work on users' machines from their own desktops. And this feature is used for managing virtualized servers and machines, including Amazon's EC2.

This particular vulnerability with Microsoft's RDP is a preauthentication one, so an attacker could get into the machine without even using credentials. "It seems rather easy to exploit, which is why they are urging [customers] to patch this as quickly as possible," Kandek says.

SANS Internet Storm Center handler Lenny Zeltser recommended that users move their RDP "listeners" to non-standard ports, rather than TCP port 3389, where it traditionally sits. "Until you install the patch, consider moving your RDP listeners to non-standard ports," Zeltser said in a SANS ISC Diary post.

Microsoft yesterday also offered up the FixIt tool for the vulnerability that lets users enable the Network Level Authentication (NLA) feature in RDP. NLA would require the attacker to authenticate to the server before trying to run an exploit, and ISC's Seltzer also recommends checking out NLA as an option.

[Remote VPN connections are not necessarily as secure as you'd think -- how enterprises can get infected by far-flung users via their SSL VPNs. See VPN An Oft-Forgotten Attack Vector. ]

Leaving RDP open basically increases your attack surface, says Rainer Enders, CTO Americas at NCP Engineering. "If you have it running, you have an active connection that can be attacked," he says. "And the way it's used, an app can be used from any machine."

Jason Miller, manager of research and development for VMware, says RDP is commonly used to connect to virtualized machines. "Although Microsoft is stating that most machines do not have RDP enabled by default, I know of many organizations that use RDP to troubleshoot machines," Miller said in a blog post. "This Windows component comes even more into play with machines that are not physically located next to users, such as virtualized machines."

He worries that the vulnerability could be exploited as a worm: "This bulletin simply scares me when it comes to protecting an environment from future attacks. This vulnerability has the real potential to become victim to a worm outbreak if this vulnerability is not patched," he said. "Although this vulnerability may be difficult to exploit, I can assure you attackers will be working hard to create a valid attack against the vulnerability."

So how can you use remote desktop access safely? Qualys' Kandek recommends adding another security control to the picture, including firewalls or first requiring a VPN log-in.

"The security battlefield today is the access device," NCP's Enders adds. "Administrators need to pay more attention [to these devices]."

Have a comment on this story? Please click "Add Your Comment" below. If you'd like to contact Dark Reading's editors directly, send us a message.

Kelly Jackson Higgins is the Executive Editor of Dark Reading. She is an award-winning veteran technology and business journalist with more than two decades of experience in reporting and editing for various publications, including Network Computing, Secure Enterprise ... View Full Bio

Comment  | 
Print  | 
More Insights
Newest First  |  Oldest First  |  Threaded View
Zero-Factor Authentication: Owning Our Data
Nick Selby, Chief Security Officer at Paxos Trust Company,  2/19/2020
44% of Security Threats Start in the Cloud
Kelly Sheridan, Staff Editor, Dark Reading,  2/19/2020
Ransomware Damage Hit $11.5B in 2019
Dark Reading Staff 2/20/2020
Register for Dark Reading Newsletters
White Papers
Current Issue
6 Emerging Cyber Threats That Enterprises Face in 2020
This Tech Digest gives an in-depth look at six emerging cyber threats that enterprises could face in 2020. Download your copy today!
Flash Poll
How Enterprises Are Developing and Maintaining Secure Applications
How Enterprises Are Developing and Maintaining Secure Applications
The concept of application security is well known, but application security testing and remediation processes remain unbalanced. Most organizations are confident in their approach to AppSec, although others seem to have no approach at all. Read this report to find out more.
Twitter Feed
Dark Reading - Bug Report
Bug Report
Enterprise Vulnerabilities
From DHS/US-CERT's National Vulnerability Database
PUBLISHED: 2020-02-21
btif/src/btif_dm.c in Android before 5.1 does not properly enforce the temporary nature of a Bluetooth pairing, which allows user-assisted remote attackers to bypass intended access restrictions via crafted Bluetooth packets after the tapping of a crafted NFC tag.
PUBLISHED: 2020-02-21
Curl before 7.49.1 in Apple OS X before macOS Sierra prior to 10.12 allows remote or local attackers to execute arbitrary code, gain sensitive information, cause denial-of-service conditions, bypass security restrictions, and perform unauthorized actions. This may aid in other attacks.
PUBLISHED: 2020-02-21
uap-core before 0.7.3 is vulnerable to a denial of service attack when processing crafted User-Agent strings. Some regexes are vulnerable to regular expression denial of service (REDoS) due to overlapping capture groups. This allows remote attackers to overload a server by setting the User-Agent hea...
PUBLISHED: 2020-02-20
Trend Micro has repackaged installers for several Trend Micro products that were found to utilize a version of an install package that had a DLL hijack vulnerability that could be exploited during a new product installation. The vulnerability was found to ONLY be exploitable during an initial produc...
PUBLISHED: 2020-02-20
The Trend Micro Security 2019 ( and below) consumer family of products is vulnerable to a denial of service (DoS) attack in which a malicious actor could manipulate a key file at a certain time during the system startup process to disable the product's malware protection functions or the ...