Getting Start

What is Computer Systems Security

A chain is only as strong as its weakest link. --木桶效应

Complex modern computer -> with great complexity comes great vulnerability

Hackers:

  • Reconnaissance

    • Little network-facing infrastructure
    • Low public profile
    • Professional external security practices

  • Gaining a foothold

    • A target

  • Internal reconnaissance

    • passive network listening
    • careful, slow active network scanning

  • Gaining influence in the network

  • Total compromise

  • Gloating

What went wrong?

  • Vulnerable network-facing infrastructure(but what could they have done?)

  • Physical security system without digital security.

  • Failure to isolate backup storage system.

  • Continued use of stale password on mailserver(and probaby others) .

  • Every-day user accounts that had Domain Administrator privileges.

  • Known vulnerability in monitoring system.

  • Link between production and development systems(probably necessary)

  • Password reuse.

  • Lack of two-factor authentication.

Computer Architecture

![](./pwn-college-getting-start/all road lead to CPU.jpg)

All roads lead to the CPU

深入到CPU中，其最本质的运算即为逻辑运算，这涉及到数电中提到的逻辑门，通过巧妙的结合这些逻辑门可以实现不同的逻辑功能，例如加法器等等。通过逻辑门复杂组合实现不同的功能，从更高角度看就构成了CPU、内存、磁盘等等器件的不同的功能。

计组里所讲的计算机内部结构