ftp servers should be excluded from this rule as this is expected behavior. some business workflows may use ftp for data exchange. these workflows often have expected characteristics such as users, sources, and destinations. ftp activity involving an unusual source or destination may be more suspicious. ftp activity involving a production server that has no known associated ftp workflow or business requirement is often suspicious.

Techniques

T1048

Sample rules

FTP (File Transfer Protocol) Activity to the Internet

source: elastic
technicques:
- T1048

Description

This rule detects events that may indicate the use of FTP network connections to the Internet. The File Transfer Protocol (FTP) has been around in its current form since the 1980s. It can be a common and efficient procedure on your network to send and receive files. Because of this, adversaries will also often use this protocol to exfiltrate data from your network or download new tools. Additionally, FTP is a plain-text protocol which, if intercepted, may expose usernames and passwords. FTP activity involving servers subject to regulations or compliance standards may be unauthorized.

Detection logic

event.category:(network or network_traffic) and network.transport:tcp and (destination.port:(20 or 21) or event.dataset:zeek.ftp) and
  source.ip:(
    10.0.0.0/8 or
    172.16.0.0/12 or
    192.168.0.0/16
  ) and
  not destination.ip:(
    10.0.0.0/8 or
    127.0.0.0/8 or
    169.254.0.0/16 or
    172.16.0.0/12 or
    192.168.0.0/16 or
    224.0.0.0/4 or
    "::1" or
    "FE80::/10" or
    "FF00::/8"
  )