Application Layer Protocol: File Transfer Protocols

Adversaries may communicate using application layer protocols associated with transferring files to avoid detection/network filtering by blending in with existing traffic. Commands to the remote system, and often the results of those commands, will be embedded within the protocol traffic between the client and server.

Protocols such as FTP, FTPS, and TFTP that transfer files may be very common in environments. Packets produced from these protocols may have many fields and headers in which data can be concealed. Data could also be concealed within the transferred files. An adversary may abuse these protocols to communicate with systems under their control within a victim network while also mimicking normal, expected traffic.

ID: T1071.002
Sub-technique of:  T1071
Platforms: Linux, Windows, macOS
Data Sources: Network Traffic: Network Traffic Content, Network Traffic: Network Traffic Flow
Version: 1.0
Created: 15 March 2020
Last Modified: 21 August 2020

Procedure Examples

ID Name Description
G0096 APT41

APT41 used exploit payloads that initiate download via FTP.[1]

S0438 Attor

Attor has used FTP protocol for C2 communication.[2]

S0465 CARROTBALL

CARROTBALL has the ability to use FTP in C2 communications.[3]

G0072 Honeybee

Honeybee uses FTP for command and control.[4]

S0201 JPIN

JPIN can communicate over FTP.[5]

S0265 Kazuar

Kazuar uses FTP and FTPS to communicate with the C2 server.[6]

G0094 Kimsuky

Kimsuky has used FTP to download additional malware to the target machine.[7]

S0409 Machete

Machete uses FTP for Command & Control.[8][9][10]

S0353 NOKKI

NOKKI has used FTP for C2 communications.[11]

S0428 PoetRAT

PoetRAT has used FTP for C2 communications.[12]

S0596 ShadowPad

ShadowPad has used FTP for C2 communications.[13]

G0083 SilverTerrier

SilverTerrier uses FTP for C2 communications.[14]

S0464 SYSCON

SYSCON has the ability to use FTP in C2 communications.[15][3]

S0161 XAgentOSX

XAgentOSX contains the ftpUpload function to use the FTPManager:uploadFile method to upload files from the target system.[16]

S0412 ZxShell

ZxShell has used FTP for C2 connections.[17]

Mitigations

ID Mitigation Description
M1031 Network Intrusion Prevention

Network intrusion detection and prevention systems that use network signatures to identify traffic for specific adversary malware can be used to mitigate activity at the network level.

Detection

Analyze network data for uncommon data flows (e.g., a client sending significantly more data than it receives from a server). Processes utilizing the network that do not normally have network communication or have never been seen before are suspicious. Analyze packet contents to detect application layer protocols that do not follow the expected protocol for the port that is being used.[18]

References