Path Interception by PATH Environment Variable
Path Interception by PATH Environment Variable [T1574.007]
Information
Name: Path Interception by PATH Environment Variable
ID: T1574.007
Technique: T1574
Introduction
Path Interception by PATH Environment Variable (T1574.007) is a sub-technique under the MITRE ATT&CK framework's Hijack Execution Flow (T1574) technique. It involves adversaries manipulating the PATH environment variable to intercept or redirect the execution flow of legitimate executables and scripts. The PATH environment variable defines directories where executable files are located, and attackers can exploit this by placing malicious executables earlier in the PATH sequence to execute their payloads instead of legitimate binaries.
Deep Dive Into Technique
The PATH environment variable is used by operating systems to locate executable files. When a user or script invokes a command without specifying the absolute path, the operating system searches directories listed in the PATH variable sequentially and executes the first matching executable it finds. Attackers exploit this behavior by inserting directories containing malicious executables at the beginning of the PATH variable.
Technical details include:
Manipulation of PATH Variable:
Attackers may alter the PATH variable by modifying user or system configuration files (e.g.,
.bashrc,.bash_profile,.profile,/etc/environment, Windows registry keys).Attackers may prepend directories to the PATH variable to ensure malicious executables are found before legitimate ones.
Malicious Executable Placement:
Attackers place malicious executables with names identical to legitimate system binaries or commonly invoked utilities (e.g.,
ls,ssh,cmd.exe,powershell.exe) into attacker-controlled directories.When the victim attempts to execute these common commands, the malicious executable runs instead.
Persistence and Privilege Escalation:
Attackers commonly use this technique for persistence—ensuring their payloads execute whenever the victim uses standard system commands.
It can also facilitate privilege escalation if higher-privileged processes inadvertently execute attacker-controlled executables.
Cross-platform Applicability:
This technique affects various operating systems including Windows, Linux, and macOS, since all rely on environment variables to locate executables.
When this Technique is Usually Used
Attackers typically employ Path Interception by PATH Environment Variable during several attack stages and scenarios, including:
Persistence:
Ensuring continued access by intercepting commonly executed commands or scripts.
Maintaining foothold after initial compromise.
Privilege Escalation:
Exploiting privileged processes or scripts that execute binaries without absolute paths, resulting in higher privileges when malicious executables are executed.
Defense Evasion:
Evading detection by executing malicious payloads through legitimate command invocations.
Bypassing application whitelisting or security controls that trust standard system executables.
Initial Access and Execution:
Leveraging user misconfigurations or insecure default settings to execute malicious payloads upon user login or script execution.
How this Technique is Usually Detected
Detection of Path Interception by PATH Environment Variable requires monitoring and analysis of environment variables, executable paths, and process execution patterns. Common detection methods include:
Monitoring Environment Variable Changes:
Track modifications to system-wide configuration files (e.g.,
/etc/profile,/etc/environment) and user-specific files (.bashrc,.bash_profile, Windows registry keys).Alert on unusual or unauthorized changes to the PATH variable.
Analyzing Executable Paths:
Monitor execution of binaries from unusual or unexpected directories.
Investigate processes executing from directories not typically containing system binaries (e.g., user home directories, temporary folders).
Endpoint Detection and Response (EDR) Tools:
Utilize EDR solutions capable of logging and alerting on suspicious process execution paths and environment changes.
Implement detection rules or behavioral analytics to identify anomalies related to PATH manipulation.
Auditing and Logging:
Enable comprehensive auditing of process creation events, especially on critical systems.
Regularly review logs for execution of binaries from non-standard locations.
Indicators of Compromise (IoCs) may include:
Unusual directories prepended to the PATH environment variable.
System commands executing from unexpected paths or directories.
Unauthorized modification of user or system configuration files.
Suspicious binaries named similarly to legitimate system executables found in unusual locations.
Why it is Important to Detect This Technique
Early detection of Path Interception by PATH Environment Variable is critical due to its potential impact on system integrity, security, and operational continuity. Possible impacts and reasons for the importance of detection include:
Persistence and Long-term Access:
Attackers can maintain persistent, stealthy access to compromised systems.
Undetected persistence mechanisms can lead to prolonged breaches and data exfiltration.
Privilege Escalation Risks:
Malicious executables executed by privileged processes can lead to unauthorized privilege escalation.
Elevated privileges enable attackers to compromise additional systems and sensitive data.
Defense Evasion and Detection Challenges:
Attackers leveraging legitimate execution flows complicate detection and attribution.
Early detection prevents attackers from hiding within legitimate system activities.
System Reliability and Stability:
Malicious executables intercepting legitimate commands can cause system instability, crashes, or unintended behaviors.
Prompt detection and remediation prevent operational disruptions.
Data and Credential Exposure:
Attackers may intercept commands that handle sensitive data, leading to credential theft or unauthorized data access.
Quick detection reduces the risk of data breaches and sensitive information exposure.
Examples
Real-world examples demonstrating Path Interception by PATH Environment Variable include:
Linux and Unix-based Scenario:
Attackers compromise a user account and modify
.bashrcor.profilefiles to prepend a malicious directory to the PATH variable.Malicious executables named after common utilities (
ssh,scp,ls) are placed in this directory.When the victim logs in and executes these commands, the malicious binaries execute first, capturing credentials or executing additional payloads.
Windows Scenario:
Attackers manipulate environment variables through registry keys (
HKCU\Environment,HKLM\SYSTEM\CurrentControlSet\Control\Session Manager\Environment) to insert malicious paths.Malicious executables named
cmd.exe,powershell.exe, or other common utilities are placed within attacker-controlled directories.When the victim or automated scripts execute these commands without specifying the absolute path, the malicious executables run instead, enabling persistence and privilege escalation.
Real-world Malware Usage:
Certain malware families, including sophisticated APT groups, have employed PATH interception to maintain persistence and evade detection.
For instance, attacker-controlled binaries have been observed intercepting SSH commands to capture credentials or execute remote commands in documented intrusion incidents.
Penetration Testing and Red Teaming Tools:
Tools such as Metasploit, Empire, and custom scripts can automate PATH interception for persistence and privilege escalation.
Red teaming exercises frequently utilize this technique to demonstrate security gaps and the importance of environment variable security.
Impacts from these examples include:
Persistent attacker access and foothold within compromised systems.
Credential theft, sensitive data exposure, and lateral movement across networks.
Privilege escalation and unauthorized administrative access.
Compromised system integrity, stability issues, and operational disruptions.
Last updated
Was this helpful?