Catching Malware With DNS As A Service

Three years ago, Jim Clark, chief technology officer of West Liberty University, had a number of IT headaches.

A botnet had resisted efforts to eradicate it from the West Virginian university's network, and students complained that Internet requests were often slow. Clark considered doubling the campus' 100-Mbps connection, but first decided to try out the free domain-name system (DNS) service offered by OpenDNS. The move to the globally available DNS service helped bring latencies on Internet requests down, and OpenDNS's increasing focus on helping customers with security helped delay the spread of the botnet until Clark's two-person information technology team could clean it out.

"In the age of bring-your-own-device ... you need to know what your network is doing, how it's breathing, and how it's performing," Clark says. "We really haven't had a botnet or malware problem since we turned it on."

While companies look to antivirus deployments and security-intelligence systems to help lock down their computers and networks, many of the features of today's DNS services can help secure the corporate network. In addition to helping speed DNS resolution, cloud-based DNS services are gaining many adherents because they give organizations better visibility into the traffic leaving their networks and the ability to filter out traffic to certain types of sites or block the command-and-control communications to known malicious sites.

[No evidence thus far to confirm that the Syrian Electronic Army embedded malware on redirected Web pages, but investigation continues. See No Proof Of Malware In New York Times DNS Hijacking Attack.]

While larger companies have the ability to deploy DNS servers in their internal networks, cloud services have quickly begun offering much of the flexibility of internal configurations while delivering on a passel of security features as well, says Patrick Foxhoven, chief technology officer for cloud security firm Zscaler.

"We see the days of deploying another security appliance on-premise are numbered," he says. "Everything that you could do on the inside, you can do as a service, especially with DNS."

Zscaler places its service as a proxy between workers' devices and requests to the Internet, so that all traffic, including DNS requests, are first sanitized through its service.

Many variants of malware, created specifically to evade detection by popular antivirus programs, still communicate to collections of domains in a way that can be detected. In September, Zscaler published an analysis of a banking Trojan known as Capshaw that used domain-generation algorithms to create pseudo-random domain names and communicate with its command-and-control servers. Other malware uses fast-flux domain resolution, which quickly changes the IP addresses assigned to a domain to hinder takedown efforts. Still other malware just communicates with known bad or relatively unknown domains. Each strategy can be detected through a cloud DNS service.

Cloud security services based on DNS also have significant benefits to companies dealing with the bring-your-own-device trend. Mobile users can still be protected, even once they have left the corporate network, says David Ulevitch, founder and CEO of OpenDNS.

"Enterprise security is predicated on having either endpoint software or network visibility," he says. "And when you have employees who have their own devices, you have no endpoint software, and when they are using it outside your network, you have no visibility."

By routing DNS traffic through a service provider's servers, mobile users retain the security benefits of the DNS proxy service without requiring that corporate IT manage the devices.

DNS services that run on internal servers cannot serve mobile users and require expensive maintenance to keep patched. While the initial cost of deploying a DNS server can be next to nothing, most companies want the reliability and extra features, says Rodney Joffe, senior vice president and fellow at domain registry and services provider Neustar. Implementing such as service inside the network means that IT is responsible for load balancing, patching, implement DNS SEC, and fending off denial-of-service attacks.

"If you are running a business, and reliability and security are important to you, then you absolutely need to use a service," he says.

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