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CyberSecurity

Personal collection of tips, tricks and ressources for cyber security.

TryHackMe is a great platform to learn cyber security! Most information are from there. I espacially recommend to get started with the AdventOfCyber.

Web

  • HTTP is stateless → (server-)session identification with cookies stored on client (i.e. web browser)

    • Cookies can only be access by sites of same domain

  • URL: subdomain.domain.TLD/ressource?param=value, i.e. www.test.de/index.html?param1=1&param2=2

  • Reverse shells:

    • Try to load and execute a reverse shell on the remote-machine!
    • Listener: sudo netcat -lvnp {port}
    • Port: use common, open ports, such as 443 or 80
    • Revere-Shell Cheatsheet
    • Upgrading a (reverse) shell:
      1. python3 -c 'import pty;pty.spawn("/bin/bash")'
      2. export TERM=xterm
      3. Ctrl + Z
      4. stty raw -echo; fg → Now you can use: tab autocomplete, arrow keys, and ctrl+c

  • BurpSuite: track http-traffic & perform dictionary attacks on websites and http-requests

    • used for fuzzing
    • Perform dictionary attacks by iterating through a list of credentials (e.g. rockyou.txt) for a specific http-request
      1. Intercept traffic by proxying through BurpSuite (use FoxyProxy extension in Firefox or build-in browser)
      2. Select request with credentials & send to "Intruder" tab
      3. Select payloads for each position
      4. Start attack
    • BurpSuite can also be used to track all network requests and drop specific requests

  • Discovering web-site directories and bruteforcing url parameters:

Other Tools

  • https://endgame.readthedocs.io/en/latest/ --> AWS Pentesting tool that lets you use one-liner commands to backdoor an AWS account's resources. Docs include top prevention and intrusion methods.
  • SQLMap: tool that automates the process of detecting and exploiting SQL injection flaws on websites
    • Install: git clone --depth 1 https://github.com/sqlmapproject/sqlmap.git sqlmap-dev
    • Cheatsheet
    • bypass WAF with --tamper=space2comment flag
    • Workflow:
      1. Submit a request on the web application we suspect to be vulnerable
      2. Intercept request with BurpSuite
      3. Send request to repeater & save request in file
      4. sqlmap -r filename → will automatically exploit database
  • XSS (Cross-Site Scripting):
    • stored XSS: store malicious js on the website, e.g. leave comment on website containing a <script> tag
    • reflected XSS (embed in url): domain.de/reflected?keyword=<script>alert(1)</script>
    • XSS Payloads: here and here
  • OWASP ZAP: open-source web application security scanner to automatically detect web vulnerabilities for a website
    • just use the automated scan
  • Preventing XSS and SQLi
    • all user input should be sanitized at both the client and server-side so that potentially malicious characters are removed
    • Smart developers should always implement a filter to any text input field and follow a strict set of rules regarding processing the inputted data, see cheatsheet
  • Wireshark: Wireshark is capable of recording a log of all the packets sent and received on a computer's network adapter
  • nmap: most important port scanning tool
    • common options: -sS | -T{0-5} | -A | -O | -sV | -Pn
    • use scripting engine to performe advanced analysis tasks:
    • protect against nmap scans with IDS & IPS Systems: Snort or Suricata. These services need to be installed on a firewall such as pfSense.
  • Server-Side Requst Forgery: vulnerability that allows attackers to force the web application server to make requests to resources it normally wouldn't
  • bypass upload filter (e.g. to upload a reverse shell script):
    • client-side filtering: block request using e.g. BurpSuite; this way, js-files can be dropped
    • server-side filtering: of often these filters fitler by file-extension. Avoid these filters by naming files as follows: FILE.jpg.php
  • VirusTotal
    • scan files, URLs, IP addresses, domains, or a file hash you provide using 60+ different Antivirus software products and displays a summary of their scan results
    • don't upload file that could contain sensitive information directly. Its better to compute the file hash (MD5) and search for file hash

Enumeration

Enumeration for priviledge escalation. Guides:

Priviledge Escalation

  • Databse of Binaries that can be used to escalate priviledges can be found here

Knowledge bases for exploits

  • most software has known vulnarabilities. These are collected in databases.
  • Vulnarabilities can be found by searching for software + version-number.
  • vulnerabilities are identified with a CVE-Number.
  • exploit-db
  • (rapid7)
  • (mitre)

Exploit known vulnarabilities with metasploit

  • first, look up a vulnarability for your version of a software in a knowledge database. Then use metasploit to exploit that vulnarabitlity.
  • start metasploit with "msfconsole -q"
  • search {CVE} → matching exploits (modules) are listet
  • "use {number}" to use a exploit
  • Now the module is loaded. Type "options" to configure the exploit.
  • type "run" to run the exploit. After finished, type "shell" to open a shell on the target machine.

Analyzing binaries

  • radare2 (for any binary): shows all functions in the binary and their assembly code

    1. r2 -d ./file1 (open binary in debug mode)
    2. aa (analyse)
    3. afl (get list of all functions)
    4. dpf @main (get assembly code of main function)
    5. step through the assembly code by using "db" (set breakpoints) and "dc" (run until breakpoint) and "ds" (execute next command)
    6. inspect variables using "px"

    Hint: Reload program using ood

  • for .NET Applications: use ILSpy (or Dotpeek). These tools show the code of .NET applications.

Windows

  • ADS: Alternate Data Stream, a file attribute specific to NTFS
    • Learn more about ADS here, here and here
    • tool to analyse a binary file (.exe): Strings.exe. Strings scans the file you pass it for strings of a default length of 3 or more characters. You can use the Strings tool to peek inside this mysterious executable file. Usage: strings64.exe -accepteula file.exe
  • Dump user password hashes with mimikatz
    • use command sekurlsa::logonpasswords to get password hashes (NTLM and SHA1 hashes)
  • All events on windows systems are logged. Also PowerShell-Script executions.
    • use FullEventLogView to conveniently few all events. (Use Advanced options for specific search.)
    • (Alternative: use windows build-in event view)

Other Tools and resources