Link Target
Link Target [T1608.005]
Information
Introduction
MITRE ATT&CK sub-technique T1608.005, "Stage Capabilities: Link Target," refers to adversaries embedding malicious payloads within shortcut files, symbolic links, or other link file types. Attackers leverage these seemingly benign files to execute malicious code or scripts when users interact with them. This technique allows adversaries to disguise their malicious intent, bypass initial suspicion, and gain initial access or persist within compromised environments.
Deep Dive Into Technique
Adversaries commonly exploit shortcut files (LNK files), symbolic links (symlinks), or other similar link files to execute malicious payloads. The technique typically involves the following execution flow:
Creation of Malicious Link Files:
Attackers craft shortcut files or symbolic links that point to malicious executables, scripts, or commands.
Malicious shortcuts are often disguised with legitimate-looking icons and filenames to appear trustworthy.
Payload Execution Mechanism:
When a user opens or interacts with the link file, the underlying malicious payload executes silently in the background.
LNK files can execute PowerShell scripts, batch files, or directly invoke malware executables.
Symbolic links can redirect to malicious locations, tricking legitimate processes into executing attacker-controlled binaries.
Common Distribution Methods:
Email-based phishing campaigns containing shortcut attachments.
Malicious downloads from compromised websites or cloud storage services.
Distribution through removable media (USB drives) containing malicious shortcuts.
Technical Advantages for Attackers:
Minimal user interaction required (often just clicking a file).
Easy evasion of simple file-type filters due to legitimate file extensions (.lnk).
Ability to leverage native operating system functionality to execute payloads, reducing suspicion.
When this Technique is Usually Used
Attackers commonly employ the "Link Target" sub-technique in various stages of the attack lifecycle, including:
Initial Access:
Phishing campaigns distributing malicious shortcut files via email attachments or malicious links.
USB drop attacks, where attackers leave malicious shortcut files on removable media in public or targeted locations.
Execution:
Shortcut files executing malicious scripts or binaries upon user interaction.
Symbolic links redirecting legitimate processes to malicious payloads.
Persistence:
Creating malicious shortcuts in startup folders to execute payloads automatically upon system reboot.
Privilege Escalation and Lateral Movement:
Using symbolic links to redirect privileged processes or services to attacker-controlled binaries.
How this Technique is Usually Detected
Detection of malicious link files involves multiple methods, tools, and indicators of compromise (IoCs):
Behavioral Monitoring and Endpoint Detection:
Monitoring endpoint activity for unusual execution of scripts or binaries triggered by shortcut files.
Utilizing endpoint detection and response (EDR) solutions to detect suspicious process chains initiated by link files.
File and Artifact Analysis:
Analyzing suspicious LNK files for embedded commands, scripts, or paths pointing to unusual directories or remote locations.
Inspecting symbolic links for abnormal redirection to suspicious or unauthorized binaries.
Network Monitoring and Intrusion Detection Systems (IDS):
Detecting outbound communication initiated by payload execution via malicious shortcuts.
Identifying anomalous network traffic patterns following user interaction with link files.
Specific Indicators of Compromise (IoCs):
LNK files containing suspicious embedded PowerShell or command-line instructions.
Shortcut files referencing unusual or temporary directories (e.g.,
%TEMP%,%APPDATA%) to execute payloads.Symbolic links redirecting to known malicious binaries or suspicious locations.
Why it is Important to Detect This Technique
Early detection of the "Link Target" sub-technique is critical due to its potential impacts and risks:
Initial Compromise:
Malicious shortcuts can provide attackers initial footholds in environments, leading to further exploitation.
Persistence and Stealth:
Attackers can establish persistent access through hidden shortcuts or symbolic links, making remediation efforts challenging.
Privilege Escalation and Lateral Movement:
Symbolic links and shortcuts can redirect privileged processes, enabling attackers to escalate privileges or move laterally within networks.
Data Exfiltration and System Damage:
Payloads executed via malicious shortcuts can lead to data theft, ransomware deployment, or destructive attacks.
Ease of Use and Popularity:
Due to the simplicity and effectiveness of this technique, attackers frequently employ it, necessitating proactive detection measures.
Examples
Real-world examples demonstrating the use of the "Link Target" sub-technique include:
Emotet Malware Campaigns:
Attackers distributed emails containing malicious shortcut (LNK) files as attachments or embedded in ZIP archives.
Users clicking these shortcuts triggered PowerShell scripts downloading and executing Emotet payloads, leading to further infections.
Agent Tesla Malware:
Attackers leveraged shortcut files disguised as legitimate documents or software installers.
Upon execution, shortcuts silently executed malicious scripts downloading and installing Agent Tesla malware, resulting in credential theft and data exfiltration.
USB Shortcut Attacks (e.g., "USB Shortcut Worm"):
Attackers placed malicious shortcut files on USB drives, leveraging autorun functionality or user interaction to execute payloads.
These attacks enabled widespread infection across multiple systems upon insertion of compromised USB devices.
APT29 (Cozy Bear) Campaigns:
APT29 utilized malicious shortcuts and symbolic links in targeted attacks to execute payloads, maintain persistence, and escalate privileges.
These attacks demonstrated sophisticated use of symbolic links redirecting legitimate processes to attacker-controlled binaries, complicating detection and remediation efforts.
Last updated
Was this helpful?