利用Shellcode进行网络安全渗透测试：复杂动作与开发概览

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"《Shellcode Development》是一份关于网络安全渗透测试中关键概念的详细介绍文档，主要关注shellcode的开发与利用。Shellcode, 在信息安全领域扮演着至关重要的角色，它是一种在漏洞探测过程中执行的代码，尤其在缓冲区溢出攻击场景中起着核心作用。传统上，shellcode的目标是通过反向连接获取被利用计算机的控制权，使得攻击者能够操控系统 shell，从而执行恶意操作。该文档首先阐述了shellcode的基本概念，指出其设计初衷是为了利用如缓冲区溢出等安全漏洞。随着技术的发展，现代shellcode不再局限于简单的控制台shell访问，而是能够执行更加复杂和多样的任务，如权限提升、数据窃取、恶意软件安装等高级攻击手法。因此，对shellcode的理解和使用在网络安全渗透测试和防御策略中变得越来越重要。 shellcode的概念可以追溯到Wikipedia的定义，以及TechTarget、SentinelOne、PCMag和Contextis等权威来源。它们详细解释了shellcode与exploit code之间的关系，即shellcode是exploit code的一部分，它负责实际执行攻击并利用系统弱点。恶意输入（malicious input）和shellcode的结合展示了黑客如何巧妙地利用这些代码来绕过防护措施，实现攻击目标。在学习和应对shellcode时，开发者和安全专业人员需要掌握编码技术、漏洞分析技巧，以及如何构建有效的防御机制来抵御shellcode攻击。这份PDF提供了深入浅出的入门指南，对希望在这个领域深入研究或从事安全工作的人员来说，是一份宝贵的参考资料。"

Shellcode Types - Remote
• Remote shellcode is used when an attacker wants to target a vulnerable process running on another machine on a local 
network, intranet, or a remote network. If successfully executed, the shellcode can provide the attacker access to the 
target machine across the network. Remote shellcodes normally use standard TCP/IP socket connections to allow the 
attacker access to the shell on the target machine. Such shellcode can be categorized based on how this connection is 
set up: if the shellcode establishes the connection, it is called a "reverse shell" or a connect-back shellcode because the 
shellcode connects back to the attacker's machine. On the other hand, if the attacker establishes the connection, the 
shellcode is called a bindshell because the shellcode binds to a certain port on the victim's machine. There's a peculiar 
shellcode named bindshell random port that skips the binding part and listens on a random port made available by 
the operating system. Because of that the bindshell random port became the smallest and stable bindshell shellcode 
for x86_64 available to this date. A third, much less common type, is socket-reuse shellcode. This type of shellcode is 
sometimes used when an exploit establishes a connection to the vulnerable process that is not closed before the 
shellcode is run. The shellcode can then re-use this connection to communicate with the attacker. Socket re-using 
shellcode is more elaborate, since the shellcode needs to find out which connection to re-use and the machine may have 
many connections open.
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• A firewall can be used to detect outgoing connections made by connect-back shellcode as well as incoming connections 
made by bindshells. They can therefore offer some protection against an attacker, even if the system is vulnerable, by 
preventing the attacker from connecting to the shell created by the shellcode. This is one reason why socket re-using 
shellcode is sometimes used: it does not create new connections and therefore is harder to detect and block.