Attacks/Breaches

1/30/2018
10:30 AM
Cricket Liu
Cricket Liu
Commentary
Connect Directly
Twitter
LinkedIn
RSS
E-Mail vvv
50%
50%

DNS Hijacking: The Silent Threat That's Putting Your Network at Risk

The technique is easy to carry out and can cause much damage. Here's what you need to know about fighting back.

In its bag of tricks, the recently discovered MaMi malware has the ability to modify the DNS configuration of an infected device. This is a good reminder that DNS hijacking is an ongoing threat that needs to be taken seriously by corporate IT organizations. DNS hijacking is easy to carry out, can be tough to detect, and is surprisingly damaging. Here's what you ought to know  and what you can do to combat it.

DNS hijacking is simple enough: one only needs to rewrite the configuration of a device on the Internet so that it sends DNS queries to malicious DNS servers. Many species of malware do this, often as just one of many consequences of infecting a device. And virtually any malware can do this — modifying DNS settings generally doesn't require any special privileges. Perhaps the most famous malware in this category is DNSChanger, which may have infected more than 4 million computers. Although DNSChanger was taken down in 2011, there are likely still hundreds of thousands of infected computers on the Internet.

So why change a device's DNS configuration? In the case of DNSChanger, it was primarily to substitute advertising on websites with advertising sold by the bad guys running the rogue DNS servers. That perhaps doesn't sound too alarming, but DNS hijacking can have much more serious effects, too. Take, for instance, the malicious DNS servers David Dagon and company discovered and wrote about in their 2008 study, "Corrupted DNS Resolution Paths: The Rise of a Malicious Resolution Authority." Dagon discovered a small but significant percentage of open recursive DNS servers on the Internet that, no matter what domain name you looked up, would always lie in the response. Some, for example, would always reply with the same set of IP addresses, none of which were the correct addresses. The address of www.nytimes.com? Addresses A, B, and C. The address of www.bankofamerica.com? That same set of addresses: A, B, and C.

What purpose could that serve? Well, it turned out that the hosts at those IP addresses (A, B and C, in our example) ran open Web proxies. As a result, users whose devices queried those DNS servers would unwittingly have all of their access to the Web directed through those open Web proxies, where their traffic could be snooped. And the DNS servers could just as easily have directed users to websites that looked identical to their bank's or brokerage's, where they'd unknowingly enter their authentication credentials and have them captured for the bad guys' later use.

Fortunately, there's a simple way to mitigate the threat of these DNS hijacking attacks: don't allow arbitrary internal IP addresses on your enterprise network to send DNS queries to arbitrary IP addresses on the Internet.

In most DNS architectures, only a subset of your DNS servers (referred to as Internet forwarders) actually need to be able to query DNS servers on the Internet. You should explicitly allow only their IP addresses to exchange DNS messages with IP addresses on the Internet. If some of your internal devices become infected with malware that modifies their DNS configurations, they'll simply stop resolving domain names, which should alert their users to the fact that something is wrong. Hopefully, that would induce them to take their devices to IT where, with any luck, the infection would be detected.

Related Content:

Cricket Liu is a leading expert on the Domain Name System (DNS) and EVP and Senior Fellow at Infoblox. With more than 25 years of experience with enterprise-scale DNS infrastructure, technical writing, training, and course development experience, Cricket serves as a liaison ... View Full Bio
Comment  | 
Print  | 
More Insights
Comments
Newest First  |  Oldest First  |  Threaded View
Facebook Aims to Make Security More Social
Kelly Sheridan, Associate Editor, Dark Reading,  2/20/2018
SEC: Companies Must Disclose More Info on Cybersecurity Attacks & Risks
Kelly Jackson Higgins, Executive Editor at Dark Reading,  2/22/2018
Register for Dark Reading Newsletters
White Papers
Video
Cartoon Contest
Write a Caption, Win a Starbucks Card! Click Here
Latest Comment: This comment is waiting for review by our moderators.
Current Issue
How to Cope with the IT Security Skills Shortage
Most enterprises don't have all the in-house skills they need to meet the rising threat from online attackers. Here are some tips on ways to beat the shortage.
Flash Poll
[Strategic Security Report] Navigating the Threat Intelligence Maze
[Strategic Security Report] Navigating the Threat Intelligence Maze
Most enterprises are using threat intel services, but many are still figuring out how to use the data they're collecting. In this Dark Reading survey we give you a look at what they're doing today - and where they hope to go.
Twitter Feed
Dark Reading - Bug Report
Bug Report
Enterprise Vulnerabilities
From DHS/US-CERT's National Vulnerability Database
CVE-2017-0290
Published: 2017-05-09
NScript in mpengine in Microsoft Malware Protection Engine with Engine Version before 1.1.13704.0, as used in Windows Defender and other products, allows remote attackers to execute arbitrary code or cause a denial of service (type confusion and application crash) via crafted JavaScript code within ...

CVE-2016-10369
Published: 2017-05-08
unixsocket.c in lxterminal through 0.3.0 insecurely uses /tmp for a socket file, allowing a local user to cause a denial of service (preventing terminal launch), or possibly have other impact (bypassing terminal access control).

CVE-2016-8202
Published: 2017-05-08
A privilege escalation vulnerability in Brocade Fibre Channel SAN products running Brocade Fabric OS (FOS) releases earlier than v7.4.1d and v8.0.1b could allow an authenticated attacker to elevate the privileges of user accounts accessing the system via command line interface. With affected version...

CVE-2016-8209
Published: 2017-05-08
Improper checks for unusual or exceptional conditions in Brocade NetIron 05.8.00 and later releases up to and including 06.1.00, when the Management Module is continuously scanned on port 22, may allow attackers to cause a denial of service (crash and reload) of the management module.

CVE-2017-0890
Published: 2017-05-08
Nextcloud Server before 11.0.3 is vulnerable to an inadequate escaping leading to a XSS vulnerability in the search module. To be exploitable a user has to write or paste malicious content into the search dialogue.