Today’s Internet intrusion detection systems (IDSes) monitor edge networks ’ DMZs to identify and/or filter malicious flows. While an IDS helps protect the hosts on its local edge network from compromise and denial of service, it cannot alone effectively intervene to halt and reverse the spreading of novel Internet worms. Generation of the worm signatures required by an IDS—the byte patterns sought in monitored traffic to identify worms—today entails non-trivial human labor, and thus significant delay: as network operators detect anomalous behavior, they communicate with one another and manually study packet traces to produce a worm signature. Yet intervention must occur early in an epidemic to halt a worm’s spread. In this paper, we describe Autograph, a system that automatically generates signatures for novel Internet worms that propagate using TCP transport. Autograph generates signatures by analyzing the prevalence of portions of flow payloads, and thus uses no knowledge of protocol semantics above the TCP level. It is designed to produce signatures that exhibit high sensitivity (high true positives) and high specificity (low false positives); our evaluation of the system on real DMZ traces validates that it achieves these goals. We extend Autograph to share port scan reports among distributed monitor instances, and using trace-driven simulation, demonstrate the value of this technique in speeding the generation of signatures for novel worms. Our results elucidate the fundamental trade-off between early generation of signatures for novel worms and the specificity of these generated signatures. 1

Network worms are a clear and growing threat to the security of today’s Internet-connected hosts and networks. The combination of the Internet’s unrestricted connectivity and widespread software homogeneity allows network pathogens to exploit tremendous parallelism in their propagation. In fact, modern worms can spread so quickly, and so widely, that no human-mediated reaction can hope to contain an outbreak. In this paper, we propose an automated approach for quickly detecting previously unknown worms and viruses based on two key behavioral characteristics – a common exploit sequence together with a range of unique sources generating infections and destinations being targeted. More importantly, our approach – called “content sifting ” – automatically generates precise signatures that can then be used to filter or moderate the spread of the worm elsewhere in the network. Using a combination of existing and novel algorithms we have developed a scalable content sifting implementation with low memory and CPU requirements. Over months of active use at UCSD, our Earlybird prototype system has automatically detected and generated signatures for all pathogens known to be active on our network as well as for several new worms and viruses which were unknown at the time our system identified them. Our initial experience suggests that, for a wide range of network pathogens, it may be practical to construct fully automated defenses – even against so-called “zero-day” epidemics. 1

This paper describes a network storage system, called Venti, intended for archival data. In this system, a unique hash of a block's contents acts as the block identifier for read and write operations. This approach enforces a write-once policy, preventing accidental or malicious destruction of data. In addition, duplicate copies of a block can be coalesced, reducing the consumption of storage and simplifying the implementation of clients. Venti is a building block for constructing a variety of storage applications such as logical backup, physical backup, and snapshot file systems.

This paper shows how to quickly move the state of a run-ning computer across a network, including the state in its disks, memory, CPU registers, and I/O devices. We call this state a capsule. Capsule state is hardware state, so it

We identify a new capability for mobile computing that mimics the opening and closing of a laptop, but avoids physical transport of hardware. Through rapid and easy personalization and depersonalization of anonymous hardware, a user is able to suspend work at one machine and to resume it at another. Our key insight is that this capability can be achieved by layering virtual machine technology on a distributed file system. We report on an initial implementation and describe our plans for improving efficiency, portability, and security.

We have implemented a secure network file system called SUNDR that guarantees the integrity of data even when malicious parties control the server. SUNDR splits storage functionality between two untrusted components, a block store and a consistency server. The block store holds all file data and most metadata. Without interpreting metadata, it presents a simple interface for clients to store variable-sized data blocks and later retrieve them by cryptographic hash.

Pangaea is a wide-area file system that supports data sharing among a community of widely distributed users. It is built on a symmetrically decentralized infrastructure that consists of commodity computers provided by the end users. Computers act autonomously to serve data to their local users. When possible, they exchange data with nearby peers to improve the system's overall performance, availability, and network economy. This approach is realized by aggressively creating a replica of a file whenever and wherever it is accessed. This paper presents

Abstract — Over the Internet today, computing and communications environments are significantly more complex and chaotic than classical distributed systems, lacking any centralized organization or hierarchical control. There has been much interest in emerging Peer-to-Peer (P2P) network overlays because they provide a good substrate for creating large-scale data sharing, content distribution and application-level multicast applications. These P2P networks try to provide a long list of features such as: selection of nearby peers, redundant storage, efficient search/location of data items, data permanence or guarantees, hierarchical naming, trust and authentication, and, anonymity. P2P networks potentially offer an efficient routing architecture that is self-organizing, massively scalable, and robust in the wide-area, combining fault tolerance, load balancing and explicit notion of locality. In this paper, we present a survey and comparison of various Structured and Unstructured P2P networks. We categorize the various schemes into these two groups in the design spectrum and discuss the application-level network performance of each group.

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and have found that it is complete and satisfactory in all respects, and that any and all revisions required by the final examining committee have been made.