Publications

Previous methods of network anomaly detection have focused on defining a temporal model of what is "normal," and flagging the "abnormal" activity that does not fit into this pre-trained construct. When monitoring traffic to and from IP addresses on a large network, this problem can become computationally complex, and potentially intractable, as a state model must be maintained for each address. In this paper, we present a method of detecting anomalous network activity without providing any historical context. By exploiting the size of the network along with the minimal overhead of NetFlow data, we are able to model groups of hosts performing similar functions to discover anomalous behavior. As a collection, these anomalies can be further described with a few high-level characterizations and we provide a means for creating and labeling these categories. We demonstrate our method on a very large-scale network consisting of 30 million unique addresses, focusing specifically on traffic related to web servers.

By accurately measuring risk for enterprise networks, attack graphs allow network defenders to understand the most critical threats and select the most effective countermeasures. This paper describes substantial enhancements to the NetSPA attack graph system required to model additional present-day threats (zero-day exploits and client-side attacks) and countermeasures (intrusion prevention systems, proxy firewalls, personal firewalls, and host-based vulnerability scans). Point-to-point reachability algorithms and structures were extensively redesigned to support "reverse" reachability computations and personal firewalls. Host-based vulnerability scans are imported and analyzed. Analysis of an operational network with 85 hosts demonstrates that client-side attacks pose a serious threat. Experiments on larger simulated networks demonstrated that NetSPA's previous excellent scaling is maintained. Less than two minutes are required to completely analyze a four-enclave simulated network with more than 40,000 hosts protected by personal firewalls.