基于Multi-agent的多用户协作垃圾邮件过滤系统的研究

基于单客户端的垃圾邮件过滤系统面对技术越来越高明的垃圾邮件发布者已经突现出它的弱点,多Agent技术为垃圾邮件过滤系统的设计提供了新的思路.旨在将Multi-agent技术和多用户协作的思想引入到垃圾邮件过滤系统中,提出了一个分布式的垃圾邮件过滤系统,使各邮件客户端能够互相协作,共享反垃圾邮件信息,从而提高单客户端垃圾邮件过滤的效果和准确率.     

基于P2P的协作式垃圾邮件检测系统

对于某一封邮件是否为垃圾邮件,很多的邮件用户可能有着相同的看法.利用这一特性,提出了一种基于P2P的协作式垃圾邮件检测系统的设计方案.系统借助的信息摘要技术,在保护用户隐私的同时,提供了较好的抗攻击能力.在邮件服务器层构建了有超级节点的P2P网络,实现了垃圾邮件信息的分布式共享.同时在用户层设计了基于多Agent的体系结构,在利用邮件服务器对收到邮件进行初步分析的结果的同时,利用个性化贝叶斯Agent,可以实现一定程度的个性化垃圾邮件检测服务.     

反垃圾邮件个垒打

近两年来，垃圾邮件大量泛滥，不断改头换面，以躲避过滤，魔高一尺；反垃圾邮件技术推陈出新，增强智能别技术，道高一丈。令人汗颜的是，垃圾邮件与病毒为伍，让传统反垃圾邮件技术措手不及。随着安全技术介入，垃圾邮件再次败下阵来。但战争并未结束，垃圾邮件时刻积续力量，准备反攻。俗话说，知己知彼，百战不殆。如若防范垃圾邮件，必须知晓垃圾邮件入侵的突破口，以及恰当的过滤手段。事实上，客户端和邮件服务器是垃圾邮件传播和落脚的根据地，如若横扫“垃圾”，必须直击客户端和邮件服务器。客户端主要靠个人用户维护，邮件服务器端则靠网管维护。现在，我们从这两个角度，讲一讲防范垃圾邮件全套攻略。     

反垃圾邮件大作战之Exchange＋Outlook篇

反垃圾和病毒邮件近几年来一直是热门话题。绝大多数的企业邮件服务器管理人员和邮箱的使用者，以及符种免赀邮箱的使用者都饱受其害。在购买商业的反垃圾邮件套件，并付诸实施之前，我们还需要自己想办法脱离苦海。幸运的是，目前各种邮件服务器或者客户端软件部已经开始提供防止垃圾邮件或者过滤垃圾邮件的功能……     

SMTVS:一种基于H.264的手机电视系统

手机电视系统必须能够适应网络和客户端的异构性、无线信道的多变性等特点.提出一种手机电视系统SMTVS,流媒体服务器在不同码率的H.264视频流之间进行切换以适应网络状况的变化;代理服务器之间构成一个内容分送网络,视频数据通过应用层组播的方式传输到各个代理服务器,降低了服务器的负载,提高了网络资源利用率;代理服务器接收到视频数据之后,针对无线链路的状况对数据进行处理后再发送到客户端,以适应最终用户的不同需求;客户端根据网络状况来动态调整播放速率,避免显示缓冲区下溢和上溢.通过流媒体服务器、代理服务器以及客户端的协作,实现了视频数据在无线信道上的自适应传输.     

反垃圾邮件网格系统的设计与实现

设计和实现了一种基于OGSA的反垃圾邮件网格系统，该系统解决了目前主流反垃圾邮件技术中存在的过于依赖服务器的缺点，通过网格对计算资源的强大整合和利用能力，为大量的反垃圾邮件计算服务。     

基于身份密码的安全电子邮件系统

针对现有电子邮件系统中的安全性问题,采用基于身份的密码体制和基于内容的过滤扫描技术,构建具有反垃圾／反病毒功能的邮件服务器及具有涉密扫描功能的邮件网关服务器,设计并实现了邮件系统客户端及其必备管理控制中心。系统具有扫描并过滤涉密邮件、加密或解密邮件、签名或认证邮件等功能,能够满足在不可控、动态和松散企业组织成员问的安全通信。     

客户端邮件软件反垃圾邮件技巧

Outlook、Outlook Express和Foxmail无疑是目前国内用户应用最广泛的三个客户端邮件管理软件,使用这些软件中的垃圾邮件管理功能，也可以帮助用户很好地将垃圾邮件分拣出来，从而起到反垃圾邮件的作用，在此整理了三位编辑在使用以上三种客户端邮件管理软件中的反垃圾邮件经验和技巧，与读者共享，     

分层垃圾邮件过滤器的设计与实现

由于垃圾邮件变化多端,日益泛滥,传统的、单一的反垃圾邮件方法对新型的垃圾邮件已经无能为力,为了攻克这一难题,我们设计了一个包含贝叶斯算法、反向DNS查询以及系统级和用户级过滤等的分层反垃圾邮件技术的邮件服务器.该服务器除了能收发邮件、过滤邮件,还可以通过自动和手动两种方式进行学习,以适应垃圾邮件的变化,有效的屏蔽垃圾邮件.本文着重介绍该服务器的垃圾过滤器所采用的各种技术和主要结构.     

突破限制 邮箱用上客户端

“Outlokk”和“Foxmail”等邮件客户端软件可以让邮件收发变得非常简单,但由于反垃圾邮件功能的“强大”,很多保存在垃圾箱内的邮件无法通过客户端来查看。另外很多邮箱服务器也不支持远程POP和SMTP功能,比如126以及网易邮箱的新注册用户。不过这样的矛盾却并不是无法调和的。下面就让我们来突破限制。让普通邮箱也用上客户端。     

Vendors Fight Spam's Sudden Rise

Companies have been complaining about spam for years, and vendors have come up with different ways to fight the deluge of unsolicited e-mail. Antispam vendors, businesses, governments, and antispam organizations are taking steps to try to stem the rising flood of unsolicited e-mail. Antispam companies are beefing up their servers and research in an effort to better and more quickly recognize spam. Businesses are also increasingly using managed antispam services, in which a company's e-mail goes through a filtering server that is often in an antispam vendor's facility. Some companies are using dedicated antispam appliances - by vendors such as Barracuda, Cisco Systems, Secure Computing, and Symantec - rather than antispam applications running on a central server. The government has set up several enforcement agencies that work together to fight spam     

一个面向移动计算设备的E-mail接收代理

移动计算设备如PDA、手机等具有资源少、网络速度慢的特点，因而其接收电子邮件的速度较慢。文中提出了采用E-mail接收代理来对电子邮件进行预处理的方法，首先根据移动计算设备的接收性能，设计一套适合于它的最佳接收规则，然后利用该规则来对它所需接收的电子邮件进行过滤、转换等操作，使得移动设备能够高效、正确地接收。此外，E-mail接收代理还可以提供诸如认证、防毒、杀毒和翻译等增值服务，进一步扩展它的应用范围。     

一个基于分布式并行过滤的前置式邮件过滤模型

提出一种新的邮件过滤模型——基于分布式并行过滤的通用前置武邮件过滤模型PDPF，由此构造的邮件过滤系统，其运行不依赖于特定的邮件服务器而在网关提供过滤服务，对到达的邮件进行并行过滤处理，其分布式并行过滤矩阵通过“并行与”操作，能够加快过滤速度。在真实环境下的实验表明，在日均邮件流量高达10万封的情况下，每封邮件的处理时间不超过50ms。     

Personalized email management at network edges

A new technique for managing and disseminating Web-based email prefetches messages and generates dynamic pages, displaying them at the network edge. Compared to other popular Web-based email servers, the prefetching and caching emails (PACE) prototype shows an improved performance with respect to user-perceived latency. Additionally, PACE'S centralized neural-network-based personalized spam filter will filter spam and viruses at the server's origin, thus saving bandwidth. Another major concern for users is the email accounts being clogged with spam. Spam filters can be classified as server-side or client-side. Server-side filters are integrated with email servers and filter out spam at the server end.     

New Spam Filtering Method with Hadoop Tuning-Based MapReduce Naïve Bayes

As the importance of email increases, the amount of malicious email is also increasing, so the need for malicious email filtering is growing. Since it is more economical to combine commodity hardware consisting of a medium server or PC with a virtual environment to use as a single server resource and filter malicious email using machine learning techniques, we used a Hadoop MapReduce framework and Naïve Bayes among machine learning methods for malicious email filtering. Naïve Bayes was selected because it is one of the top machine learning methods(Support Vector Machine (SVM), Naïve Bayes, K-Nearest Neighbor(KNN), and Decision Tree) in terms of execution time and accuracy. Malicious email was filtered with MapReduce programming using the Naïve Bayes technique, which is a supervised machine learning method, in a Hadoop framework with optimized performance and also with the Python program technique with the Naïve Bayes technique applied in a bare metal server environment with the Hadoop environment not applied. According to the results of a comparison of the accuracy and predictive error rates of the two methods, the Hadoop MapReduce Naïve Bayes method improved the accuracy of spam and ham email identification 1.11 times and the prediction error rate 14.13 times compared to the non-Hadoop Python Naïve Bayes method.     

基于主动探测的非关系型数据库风险感知系统设计与实现

Elastic数据库是一款主流的非关系型数据库,默认安装时存在潜在的信息泄露风险。本文基于网络主动探测技术,设计实现了一个Elastic数据库风险感知系统。系统首先通过协议构造实现Elastic服务器上各类信息的获取,然后设计了一种基于手机号码、邮箱地址、身份证号、地名地址等多维数据协同分析的敏感信息检测方法,从而评估数据库风险等级并进行预警。本文最后进行了敏感数据检测测试及总体功能测试,实验结果表明了本文敏感信息检测方法及系统设计实现的有效性。     

网络机房服务器监控平台的构建

利用开源软件Nagios构建服务器性能监控平台,对高校机房服务器的网络。关键应用和硬件主要指标进行Web可视化监控,把故障信息通过电子邮件和手机短信实时通知系统管理员。重点介绍了监控平台实现的基本原理和安装配置,并结合本校实际给出案例。     

Mobile collaborative medical display system

Because of recent advances in wireless communication technologies, the world of mobile computing is flourishing with a variety of applications. In this study, we present an integrated architecture for a personal digital assistant (PDA)-based mobile medical display system that supports collaborative work between remote users. We aim to develop a system that enables users in different regions to share a working environment for collaborative visualization with the potential for exploring huge medical datasets. Our system consists of three major components: mobile client, gateway, and parallel rendering server. The mobile client serves as a front end and enables users to choose the visualization and control parameters interactively and cooperatively. The gateway handles requests and responses between mobile clients and the rendering server for efficient communication. Through the gateway, it is possible to share working environments between users, allowing them to work together in computer supported cooperative work (CSCW) mode. Finally, the parallel rendering server is responsible for performing heavy visualization tasks. Our experience indicates that some features currently available to our mobile clients for collaborative scientific visualization are limited due to the poor performance of mobile devices and the low bandwidth of wireless connections. However, as mobile devices and wireless network systems are experiencing considerable elevation in their capabilities, we believe that our methodology will be utilized effectively in building quite responsive, useful mobile collaborative medical systems in the very near future.     

A Dynamic Shadow Approach to Fault-Tolerant Mobile Agents in an Autonomic Environment

Large-scale distributed applications such as online information retrieval and collaboration over computational elements demand an approach to self-managed computing systems with a minimum of human interference. However, large scales and full distribution often lead to poor system dependability and security, and increase the difficulty in managing and controlling redundancy for fault tolerance. In particular, fault tolerance schemes for mobile agents to survive agent server crash failures in an autonomie environment are complex since developers normally have no control over remote agent servers. Some solutions inject a replica into stable storage upon its arrival at an agent server. But in the event of an agent server crash the replica is unavailable until the agent server recovers. In this paper we present a failure model and an exception handling framework for mobile agent systems. An exception handling scheme is developed for mobile agents to survive agent server crash failures. A replica mobile agent operates at the agent server visited prior to its master's current location. If a master crashes its replica is available as a replacement. The proposed scheme is examined in comparison with a simple time-out scheme. Experimental evaluation is performed, and performance results show that the scheme leads to some overhead in the round trip time when fault tolerance measures are exercised. However the scheme offers the advantage that fault tolerance is provided during the mobile agent trip, i.e. in the event of an agent server crash all agent servers are not revisited.