企业邮件安全及深层防御方法研究

发布时间：2018-04-03 03:09

本文选题：邮件系统安全　切入点：反垃圾邮件　出处：《上海交通大学》2014年硕士论文

【摘要】：随着互联网技术的发展,电子邮件在企业中被广泛应用。邮件系统的安全问题受到越来越多的关注。我们都知道,信息安全的三要素保密性,完整性,可用性是作为衡量邮件系统安全的基本标准。目前,这个基准正受到严重的挑战。威胁企业邮件系统安全的两大因素:垃圾邮件和基于SMTP的缺陷攻击。一方面,最终用户每天接收到大量的垃圾邮件;导致用户邮箱中大量的存储空间被垃圾邮件占用。这是一种非常严重的资源浪费。另一方面,针对SMTP协议的漏洞攻击对企业邮件服务的可用性和保密性产生了极大的负面影响。因此,保证邮件流的安全和反垃圾邮件是成为企业系统安全的核心问题。本论文论述邮件系统安全和反垃圾邮件对企业的重要价值。介绍:1.邮件在企业中如何工作;2.垃圾邮件的目的;3.垃圾邮件的定义;4.垃圾邮件种类;然后,本文遵循发现问题--分析问题--解决问题原则。发现问题:通过阅读了大量国内外信息安全资料,分析了现有企业邮件系统方案不足(现在企业邮件系统的安全方案:灰名单,DNS反向解析(PTR),验证码仔细)并总结了SMTP协议的缺陷。提出了现在企业遇到的棘手的四个问题:大量垃圾邮件攻击,伪造邮件,基于NDR的SPAM攻击,账户密码泄露。分析问题:以一个企业邮件系统为实例,使用上面提到的4种方法,进行模拟攻击。在分析问题的方法上用到了实验,模拟,定量,定性。解决问题:然后基于分析和实际测试的结果,提出了具体的理论方案(延迟技术,非强制PTR记录,收件人名单比较,服务器之间的安全加密)。1.延迟技术:从源头堵住大量邮件地址搜索。在邮件服务器上对所有的请求响应延迟接受从而避免或者减少邮件地址搜索。2.非强制PTR记录:避免了PTR记录的非黑即白的方案,而是使用了相对放松并且安全的方式。3.收件人名单比较:通过搭建一台服务器,实现只在收件人名单中有的用户才能收到邮件。4.服务器之间的安全加密:提出内部服务器安全的概念,避免因轻视内部服务器之间的安全而带来的问题。实验和实验数据:为了让理论方案得以实现,我们用微软邮件服务器Exchange Server和免费平台的邮件服务器进行了模拟测试并统计测试结果。提出了邮件系统的深层防御解决方案并提供了实验室数据:1.大批量邮件攻击防御2.假冒发件人攻击防御3.不存在收件人攻击防御4.信息截取防御最后,本论文从具体问题的解决方案升华到具有普遍意义的解决方法,提出了分层次的安全防御策略。通过多层次的安全防御方案的整合,提高了企业邮件系统的防御能力。并指出未来邮件系统安全的一种发展趋势:云邮件安全系统。
[Abstract]:With the development of Internet technology, e-mail is widely used in enterprises.More and more attention has been paid to the security of mail system.As we all know, the three elements of information security confidentiality, integrity and availability are the basic criteria to measure the security of mail systems.At present, this benchmark is being seriously challenged.Two major threats to the security of corporate mail systems are spam and SMTP-based flaw attacks.On the one hand, the end user receives a large amount of spam every day, which results in a large amount of storage space occupied by spam.This is a very serious waste of resources.On the other hand, the vulnerability attack against SMTP protocol has a great negative impact on the availability and confidentiality of enterprise mail service.Therefore, to ensure the security of mail flow and anti-spam is the core issue of enterprise system security.This paper discusses the important value of mail system security and anti-spam to enterprises.Introduce one.How mail works in an enterprise.The purpose of spam is 3.The definition of spam is 4. 4.Type of spam; then, this article follows the principle of problem discovery-analysis-problem-solving.Problem finding: by reading a large number of information security materials at home and abroad,This paper analyzes the deficiency of the existing enterprise mail system (the security scheme of the enterprise mail system now: the grey list SMTP reverse parsing, the verification code is careful) and summarizes the defects of the SMTP protocol.This paper puts forward four thorny problems that enterprises are confronted with: a large number of spam attacks, forged emails, SPAM attacks based on NDR, and account password leaks.Analysis problem: take an enterprise mail system as an example, use the four methods mentioned above to simulate the attack.Experiments, simulations, quantification, and qualitative analysis are used to analyze the problem.Solve the problem: then based on the results of analysis and practical testing, we propose a specific theoretical scheme (delay technology, non-mandatory PTR records, recipient list comparison, security encryption between servers.Delay technique: blocking a large number of mail address searches from the source.Delay acceptance of all requests on the mail server to avoid or reduce mail address search. 2. 2.Non-mandatory PTR records: avoids the black or white scheme for PTR records, but uses a relatively relaxed and secure approach. 3.Recipient list comparison: by setting up a server, only users on the recipient list can receive mail. 4.Security encryption between servers: the concept of internal server security is proposed to avoid the problems caused by despising the security between internal servers.Experiment and experiment data: in order to realize the theoretical scheme, we use Microsoft mail server Exchange Server and the mail server of free platform to carry on the simulation test and statistics the test result.A deep defense solution for the mail system is proposed and the laboratory data: 1. 1 is provided.Mass mail attack defense 2.Fake Sender attack Defense 3.There is no recipient attack defense 4.Finally, this paper sublimates the solution from the concrete problem to the solution with universal significance, and puts forward the security defense strategy of different levels.Through the integration of multi-level security defense scheme, the defense ability of enterprise mail system is improved.And point out a kind of development trend of mail system security in the future: cloud mail security system.
【学位授予单位】：上海交通大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TP393.098

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