Fighting Botnets in an Internet Service Provider Environment

Botnets are compromised hosts under a common command and control infrastructure. These nets have become very popular because of their potential for various malicious activity. They are frequently used for distributed denial-of-service attacks, spamming, spreading malware and privacy invasion. Manually uncovering and responding to such hosts is difficult and costly. In this thesis a technique for uncovering and reporting botnet activity in an internet service provider environment is presented and tested. Using a list of known botnet controllers, an ISP can proactivly warn customers of likely compromised hosts while at the same time mitigate future ill-effects by severing communications between the compromised host and the controller. A prototype system is developed to route traffic destined for controllers to a sinkhole host, then analyse and drop the traffic. After using the system in a live environment at the norwegian reasearch and education network the technique has proven to be a feasable one, and is used in a incident response test-case, warning two big customers of likely compromised hosts. However, there are challenges in tracking down and following up such hosts, especially ``roaming'' hosts such as laptops. The scope of the problem is found to be serious, with the expected number of new hosts found to be about 75 per day. Considering that the list used represents only part of the actual controllers active on the internet, the need for an automated incident response seems clear