Abstract. In this paper, we present an accurate and realtime PE-Miner framework that automatically extracts distinguishing features from portable executables (PE) to detect zero-day (i.e. previously unknown) malware. The distinguishing features are extracted using the structural information standardized by the Microsoft Windows operating system for executables, DLLs and object files. We follow a threefold research methodology: (1) identify a set of structural features for PE files which is computable in realtime, (2) use an efficient preprocessor for removing redundancy in the features' set, and (3) select an efficient data mining algorithm for final classification between benign and malicious executables. We have evaluated PE-Miner on two malware collections, VX Heavens and Malfease datasets which contain about 11 and 5 thousand malicious PE files respectively. The results of our experiments show that PE-Miner achieves more than 99% detection rate with less than 0.5% false alarm rate for distinguishing between benign and malicious executables. PEMiner has low processing overheads and takes only 0.244 seconds on the average to scan a given PE file. Finally, we evaluate the robustness and reliability of PE-Miner under several regression tests. Our results show that the extracted features are robust to different packing techniques and PE-Miner is also resilient to majority of crafty evasion strategies.

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Real-time Anomaly Detection Systems (ADSs) use packet sampling to realize traffic analysis at wire speeds. While recent studies have shown that a considerable loss of anomaly detection accuracy is incurred due to sampling, solutions to mitigate this loss are largely unexplored. In this paper, we propose a Progressive Security-Aware Packet Sampling (PSAS) algorithm which enables a real-time inline anomaly detector to achieve higher accuracy by sampling larger volumes of malicious traffic than random sampling, while adhering to a given sampling budget. High malicious sampling rates are achieved by deploying inline ADSs progressively on a packet's path. Each ADS encodes a binary score (malicious or benign) of a sampled packet into the packet before forwarding it to the next hop node. The next hop node then samples packets marked as malicious with a higher probability. We analytically prove that under certain realistic conditions, irrespective of the intrusion detection algorithm used to formulate the packet score, PSAS always provides higher malicious packet sampling rates. To empirically evaluate the proposed PSAS algorithm, we simultaneously collect an Internet traffic dataset containing DoS and portscan attacks at three different deployment points in our university's network. Experimental results using four existing anomaly detectors show that PSAS, while having no extra communication overhead and extremely low complexity, allows these detectors to achieve significantly higher accuracies than those operating on random packet samples.