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Compromise Client Software Binary

Adversaries may modify client software binaries to establish persistent access to systems. Client software enables users to access services provided by a server. Common client software types are SSH clients, FTP clients, email clients, and web browsers.

Adversaries may make modifications to client software binaries to carry out malicious tasks when those applications are in use. For example, an adversary may copy source code for the client software, add a backdoor, compile for the target, and replace the legitimate application binary (or support files) with the backdoored one. Since these applications may be routinely executed by the user, the adversary can leverage this for persistent access to the host.

ID: T1554
Sub-techniques:  No sub-techniques
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Tactic: Persistence
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Platforms: Linux, Windows, macOS
Contributors: CrowdStrike Falcon OverWatch
Version: 1.0
Created: 11 February 2020
Last Modified: 19 October 2021

Procedure Examples

ID Name Description
S0486 Bonadan

Bonadan has maliciously altered the OpenSSH binary on targeted systems to create a backdoor.[1]
S0377 Ebury

Ebury has been embedded into modified OpenSSH binaries to gain persistent access to SSH credential information.[2]
S0604 Industroyer

Industroyer has used a Trojanized version of the Windows Notepad application for an additional backdoor persistence mechanism.[3]
S0487 Kessel

Kessel has maliciously altered the OpenSSH binary on targeted systems to create a backdoor.[1]
S0641 Kobalos

Kobalos replaced the SSH client with a trojanized SSH client to steal credentials on compromised systems.[4]
S0595 ThiefQuest

ThiefQuest searches through the /Users/ folder looking for executable files. For each executable, ThiefQuest prepends a copy of itself to the beginning of the file. When the file is executed, the ThiefQuest code is executed first. ThiefQuest creates a hidden file, copies the original target executable to the file, then executes the new hidden file to maintain the appearance of normal behavior. [5][6]
S0658 XCSSET

XCSSET uses a malicious browser application to replace the legitimate browser in order to continuously capture credentials, monitor web traffic, and download additional modules.[7]

Mitigations

ID Mitigation Description
M1045 Code Signing

Ensure all application component binaries are signed by the correct application developers.

Detection

ID Data Source Data Component
DS0022 File File Creation
File Deletion
File Metadata
File Modification

Collect and analyze signing certificate metadata and check signature validity on software that executes within the environment. Look for changes to client software that do not correlate with known software or patch cycles.

Consider monitoring for anomalous behavior from client applications, such as atypical module loads, file reads/writes, or network connections.

References

  1. Dumont, R., M.Léveillé, M., Porcher, H. (2018, December 1). THE DARK SIDE OF THE FORSSHE A landscape of OpenSSH backdoors. Retrieved July 16, 2020.
  2. M.Léveillé, M.. (2014, February 21). An In-depth Analysis of Linux/Ebury. Retrieved April 19, 2019.
  3. Anton Cherepanov. (2017, June 12). Win32/Industroyer: A new threat for industrial controls systems. Retrieved December 18, 2020.
  4. M.Leveille, M., Sanmillan, I. (2021, January). A WILD KOBALOS APPEARS Tricksy Linux malware goes after HPCs. Retrieved August 24, 2021.
  1. Patrick Wardle. (2020, July 3). OSX.EvilQuest Uncovered part ii: insidious capabilities. Retrieved March 21, 2021.
  2. Thomas Reed. (2020, July 7). Mac ThiefQuest malware may not be ransomware after all. Retrieved March 22, 2021.
  3. Mac Threat Response, Mobile Research Team. (2020, August 13). The XCSSET Malware: Inserts Malicious Code Into Xcode Projects, Performs UXSS Backdoor Planting in Safari, and Leverages Two Zero-day Exploits. Retrieved October 5, 2021.