tools

Overview

Telnet is an insecure plaintext protocol used to establish raw TCP connections to remote hosts and services. While largely replaced by SSH for remote administration, Telnet remains useful for manually interacting with and testing network services such as HTTP, SMTP, POP3, and FTP.

Target / Context

Any service accepting raw TCP connections — commonly used for banner grabbing and manual protocol testing during recon.

Installation

ℹ︎Installation Commands:

Pre-installed on most Linux systems.

sudo apt install telnet

Basic Usage

ℹ︎Basic Usage: 
telnet <IP> <PORT>

Establishes a raw TCP connection to the specified host and port. Supports anonymous login on some services.

Flags & Options

ℹ︎Flags & Options:
FlagDescriptionExample
IPTarget IP address or hostnametelnet 10.10.10.1
PORTTarget port numbertelnet 10.10.10.1 80

Common Use Cases

Manual HTTP Request

Connect to port 80 and send a raw HTTP request.

ℹ︎Commands: 
telnet <IP> 80

Then type:

GET /file HTTP/1.1

Then type:

Host: anything

SMTP Testing

Connect to port 25 and interact with the mail server.

ℹ︎Commands: 
telnet <IP> 25

See Protocols for SMTP commands (HELO, MAIL FROM, DATA etc.)

POP3 Testing

Connect to port 110 and interact with mail retrieval.

ℹ︎Commands: 
telnet <IP> 110

See Protocols for POP3 commands (USER, PASS, LIST, RETR etc.)

FTP-style File Navigation

FTP commands sent over the Telnet connection — not native Telnet commands.

ℹ︎Commands:

List files in current directory

ls

Retrieve a file

get <filename>

Upload a file

put <filename>

Change directory

cd <directory>

References / Images