21-FTP

The File Transfer Protocol (FTP) is a standard communication protocol used for transferring computer files between a server and a client on a network. It operates as a clear-text protocol, meaning that data is sent in an unencrypted format.

Default Port: 21

Banner grabbing

nc -nv $IP 21
 
# Get certificate if any
openssl s_client -connect $IP:21 -starttls ftp

Nmap

Nmap is a network scanner created by Gordon Lyon. Nmap is used to discover hosts and services on computer network by sending packets and analyzing the responses.

Nmap provides a number of features for probing computer networks, including host discovery and service and operating system detection.

# Enum FTP with all NSE
sudo nmap -p21 --script=ftp-* $IP
 
# Perform brute-force
sudo nmap -p21 --script=ftp-brute --script-args userdb=/wordlists/users.txt $IP

FTP command

FTP is the user interface to the Internet standard File Transfer Protocol. The program allows a user to transfer files to and from a remote network site.

ftp $IP
>anonymous        # Username
>anonymous        # Password
> status          # Show current status
> ls -a           # List hidden files
> ls -R           # Recursively listing files
> get file.txt    # Download a file (file.txt)
> put file.txt    # Upload a file (file.txt)
> exit            # Exit 

Download all files (recursively)

wget -m ftp://'anonymous:anonymous'@$IP
wget -m --no-passive ftp://'anonymous:anonymous'@$IP

Hydra

Hydra is a parallelized login cracker which supports numerous protocols to attack. It is very fast and flexible, and new modules are easy to add.

Link to original

hydra -L /wordlists.txt/users.txt -P /wordlists/passwords.txt $IP ftp

Metasploit Framework

Metasploit Framework is an open source platform that supports vulnerability research, exploit development, and the creation of custom security tools.

Link to original

auxiliary/scanner/ftp/ftp_version          # ftp version enumeration
auxiliary/scanner/ftp/anonymous            # check for anonymous login
auxiliary/scanner/ftp/ftp_login            # ftp brute-force
exploit/unix/ftp/vsftpd_234_backdoor       # vsftpd v2.3.4 (exploit)

Config files

# vsFTPd config file
cat /etc/vsftpd.conf | grep -v "#"
 
# List users can't access to FTP
cat /etc/ftpusers

Dangerous settings

Different security settings can be applied to an FTP server. One such authentication method is anonymous access. For vsFTPd, the optional settings that can be added to the configuration file for the anonymous login look like this:

Setting	Description
anonymous_enable=YES	Allowing anonymous login?
anon_upload_enable=YES	Allowing anonymous to upload files?
anon_mkdir_write_enable=YES	Allowing anonymous to create new directories?
no_anon_password=YES	Do not ask anonymous for password?
anon_root=/home/username/ftp	Directory for anonymous.
write_enable=YES	Allow the usage of FTP commands: STOR, DELE, RNFR, RNTO, MKD, RMD, APPE, and SITE?
hide_ids=NO	User and group IDs are visible, instead of displayed as “ftp”.