In part 1, I talked about some of the risks associated with BYOD. But there are actions you can take to greatly reduce this risk. One effective method for limiting the risk of BYOD is to employ DNS-based security intelligence techniques. DNS-based security intelligence makes use of an enterprise's caching DNS server to monitor and block DNS queries to known botnet command and control (C&C) domains. These domains are the domain names of the servers that are in the control of the bot master for purposes of botnet command and control. Bots will perform a DNS query for one or more of these domains in an attempt to connect to these servers in order to receive their instructions. By monitoring queries to these domains, all infected clients, including BYOD, can be identified on the network. Moreover, by subsequently blocking access to the domains, malware responsible for the bot infection is denied the critical instructions it needs to function.
As DNS is the first touch point in any Internet transaction, using it to identify infected customers is both lightweight and cost effective since it only has to deal with relatively small DNS packets. If you have a list of known botnet command and control domains, you can determine which clients (including BYOD clients) are infected on your network by comparing that list to your DNS logs. You can also use this list to configure your DNS server to block any queries to these domains, which denies the bots the instructions they need in order to conduct their malicious activity.
Using this DNS-based technique, Nominum recently reported on the top 5 mobile malware threats which has been published by Network World. These Android infections could be lurking on your network's wi-fi as BYOD. If you want to quickly try out this DNS-based technique for yourself to see what might be lurking on your network, you can try out one of the lists of known botnet C&C domains maintained by The Shadowserver Foundation.
BYOD is a great thing, but it can be scary for those folks responsible for the security of an enterprise. Using DNS-based techniques for security intelligence can stem the risk of BYOD, which is good since revoking BYOD would likely sow the seeds aof revolt.
By Pat Barnes, Product Manager of Security Solutions at Nominum
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