January 2021
Intermediate to advanced
547 pages
12h 4m
Chinese
Content preview from 网络安全评估（第三版）
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电子邮件服务评估
｜
317
邮件服务应对措施
对邮件系统进行加固时，应考虑如下应对措施：
•
不要将功能丰富的
SMTP
服务器暴露给公众
Internet
或非可信网络。
Sendmail
和
Microsoft Exchange
代码规模庞大，其中引入了很多不必要的
暴露接口。可以使用专用的内容过滤器（物理设备或云服务）对电子邮件
进行分析，或部署使用轻量级
MTA
，比如
qmail
或
Exim
。
•
使用
SPF
、
DKIM
和
DMARC
防止邮件服务器传输和接收未授权内容，并
将暴露的
SMTP
接口配置为不接受来自非信任网络（如公众
Internet
）的
电子邮件，即便这些邮件看起来似乎来自组织网络的内部域。
•
对外部的内容过滤机制进行配置，使其在预期外的电子邮件主体字段中添
加相应描述（如添加一个字符串，通知用户本消息来自不可信源）。
•
使用防病毒和内容过滤软件会增加攻击面，这些软件包存在可利用漏洞，
要确保其升级更新了最新补丁程序。
•
禁用邮件服务对弱认证机制的支持（比如
LOGIN
、
PLAIN
、
CRAM-MD5
等），
如果
SMTP
没有使用认证机制，则对其完全禁用。
•
可能的地方强制使用
TLS
（在
SMTP
服务器之间，以及支持通过
POP3
和
IMAP
协议收发电子邮件的服务之间）。
•
在邮件服务器中实施强口令策略，以便最小化口令暴力破解攻击的影响。
•
对针对邮件服务的失败认证尝试进行记录，增强对攻击行为的可视性。在
Microsoft Windows
等平台中，可以对账号锁定策略进行定义和实施，以
规避口令暴力破解攻击的风险。
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O’Reilly covers everything we've got, with content to help us build a world-class technology community, upgrade the capabilities and competencies of our teams, and improve overall team performance as well as their engagement.Julian F.
I wanted to learn C and C++, but it didn't click for me until I picked up an O'Reilly book. When I went on the O’Reilly platform, I was astonished to find all the books there, plus live events and sandboxes so you could play around with the technology.Addison B.
I’ve been on the O’Reilly platform for more than eight years. I use a couple of learning platforms, but I'm on O'Reilly more than anybody else. When you're there, you start learning. I'm never disappointed.Amir M.
I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.