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.

Vulnerabilities / Threats

6/15/2016
08:00 AM
Connect Directly
Twitter
RSS
E-Mail
50%
50%

Windows 'BadTunnel' Attack Hijacks Network Traffic

Newly discovered -- and now patched -- Windows design flaw affects all versions of Windows.

A researcher in China has discovered a design flaw in Microsoft Windows that affects all versions of the operating system—including Windows 10—and lets an attacker hijack a victim organization’s network traffic.

Microsoft this week issued a patch for the so-called “BadTunnel” bug found by Yang Yu, director of Xuanwu Lab of Tencent in Beijing. Yu will detail and demonstrate his findings on the Windows flaw in August at Black Hat USA in Las Vegas in his presentation BadTunnel: How Do I Get Big Brother Power? 

“This vulnerability has a massive security impact – probably the widest impact in the history of Windows,” Yu said an an interview with Dark Reading conducted via email. “It not only can be exploited through many different channels, but also exists in all Windows versions released during the past 20 years. It can be exploited silently with a near perfect success rate.”

BadTunnel isn’t a typical coding-error flaw: it’s a combination of issues that together allow for an exploit. “This vulnerability is caused by a series of seemingly correct implementations, which includes a transport layer protocol, an application layer protocol, a few specific usage of application protocol by the operating system, and several protocol implementations used by firewalls and NAT devices,” Yu explains.

It can be exploited via all versions of Microsoft Office, Edge, Internet Explorer, and via several third-party apps on Windows, he says. Unlike most attacks, it doesn’t even require malware, although an attacker could deploy malware as well, he says. That makes it even more difficult to detect when a BadTunnel attack is under way, he notes. An attacker could also execute the attack via IIS and Apache Web servers, as well as via a thumb drive.

Yu says BadTunnel is basically a technique for NetBIOS-spoofing across networks: the attacker can get access to network traffic without being on the victim’s network, and also bypass firewall and Network Address Translation (NAT) devices.  

It basically works like this: the attacker gets a victim to visit a rigged web page via IE or Edge, or to open a rigged Office document (or install a malicious flash drive). The attacker’s site appears as either a file server or a local print server, and hijacks the victim’s network traffic – HTTP, Windows Updates, and even Certificated Revocation List updates via Microsoft’s CryptoAPI.

BadTunnel exploits a series of security weaknesses, including how Windows resolves network names and accepts responses; how  IE and Edge browsers support webpages with embedded content; how Windows handles network paths via an IP address; how NetBIOS Name Service NB and NBSTAT queries handle transactions; and how Windows handles queries on the same UDP port (137) -- all of which when lumped together make the network vulnerable to a BadTunnel attack.

Here’s an attack scenario, as explained in Yu’s technical paper:

1.  Alice and Bob can be located anywhere on their network, and have firewall and NAT devices in-between, as long as Bob’s 137/UDP port is reachable by Alice.

2.  Bob closes 139 and 445 port, but listens on 137/UDP port.

3.  Alice is convinced to access a file URI or UNC path that points to Bob, and another hostname based URI such as “http://WPAD/x.jpg” or “http://FileServer/x.jpg”. Alice will send a NBNS NBSTAT query to Bob, and also send a NBNS NB query to the LAN broadcast address.

4.  If Bob blocks access to 139 and 445 port using a firewall, Alice will send a NBNS NBSTAT query after approximately 22 seconds. If Bob instead closed 139 and 445 port by disabling Server Windows service or NetBIOS over TCP/IP protocol, Alice do not need to wait for connection to time out before send the query.

5.  When Bob received NBNS NBSTAT query sent by Alice, Bob forge a NBNS NB response by predicting the transaction id, and send to Alice. If a heartbeat packet is sent every few second, most firewall and NAT devices will keep the 137/UDP<->137/UDP tunnel open.

6.  Alice will now add the resolved address sent by Bob to the NBT cache. The default TTL for NBT cache entry is 600 seconds.

Bob then hijacks Alice’s network traffic by posing as a Web Proxy Auto-Discovery Protocol (WPAD) or Intra-Site Automatic Tunnel Addressing Protocol (ISATAP) server. WPAD hijacking is nothing new, Yu notes: HD Moore & Valsmith presented research on this in 2007 at Black Hat USA, and the Flame worm employed a similar attack method.

Black Hat USA returns to the fabulous Mandalay Bay in Las Vegas, Nevada July 30 through Aug. 4, 2016. Click for information on the conference schedule and to register.

 

Yu says his discovery of BadTunnel began during a flight last year. “One day last year, when I was on an airplane, I got bored. I started to imagine different security problems and suddenly came up with a brand new attack scenario,” he recalls. “After the trip, I immediately started testing on different system configurations, and finally discovered this vulnerability in the Windows operating system.”

Yu first reported his finding to Microsoft in January, he says. He says he’s not aware of any attacks in the wild.

His advice to Windows users: “For the average user, always make sure you have the latest available patches. If for some reason you can not install the patch, I suggest you disable the NetBIOS over TCP/IP to prevent BadTunnel attack,” he says.

Related Content:

 

 

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
 

Recommended Reading:

Comment  | 
Print  | 
More Insights
Comments
Newest First  |  Oldest First  |  Threaded View
Frankie89
50%
50%
Frankie89,
User Rank: Apprentice
5/9/2017 | 5:18:59 PM
The security of homepages
really great post but at the and the weak spot is always the bad informed user
News
Former CISA Director Chris Krebs Discusses Risk Management & Threat Intel
Kelly Sheridan, Staff Editor, Dark Reading,  2/23/2021
Edge-DRsplash-10-edge-articles
Security + Fraud Protection: Your One-Two Punch Against Cyberattacks
Joshua Goldfarb, Director of Product Management at F5,  2/23/2021
News
Cybercrime Groups More Prolific, Focus on Healthcare in 2020
Robert Lemos, Contributing Writer,  2/22/2021
Register for Dark Reading Newsletters
White Papers
Video
Cartoon Contest
Current Issue
2021 Top Enterprise IT Trends
We've identified the key trends that are poised to impact the IT landscape in 2021. Find out why they're important and how they will affect you today!
Flash Poll
Building the SOC of the Future
Building the SOC of the Future
Digital transformation, cloud-focused attacks, and a worldwide pandemic. The past year has changed the way business works and the way security teams operate. There is no going back.
Twitter Feed
Dark Reading - Bug Report
Bug Report
Enterprise Vulnerabilities
From DHS/US-CERT's National Vulnerability Database
CVE-2021-22861
PUBLISHED: 2021-03-03
An improper access control vulnerability was identified in GitHub Enterprise Server that allowed authenticated users of the instance to gain write access to unauthorized repositories via specifically crafted pull requests and REST API requests. An attacker would need to be able to fork the targeted ...
CVE-2021-22862
PUBLISHED: 2021-03-03
An improper access control vulnerability was identified in GitHub Enterprise Server that allowed an authenticated user with the ability to fork a repository to disclose Actions secrets for the parent repository of the fork. This vulnerability existed due to a flaw that allowed the base reference of ...
CVE-2021-22863
PUBLISHED: 2021-03-03
An improper access control vulnerability was identified in the GitHub Enterprise Server GraphQL API that allowed authenticated users of the instance to modify the maintainer collaboration permission of a pull request without proper authorization. By exploiting this vulnerability, an attacker would b...
CVE-2020-10519
PUBLISHED: 2021-03-03
A remote code execution vulnerability was identified in GitHub Enterprise Server that could be exploited when building a GitHub Pages site. User-controlled configuration of the underlying parsers used by GitHub Pages were not sufficiently restricted and made it possible to execute commands on the Gi...
CVE-2021-21353
PUBLISHED: 2021-03-03
Pug is an npm package which is a high-performance template engine. In pug before version 3.0.1, if a remote attacker was able to control the `pretty` option of the pug compiler, e.g. if you spread a user provided object such as the query parameters of a request into the pug template inputs, it was p...