Windows Command Shell
Windows Command Shell [T1059.003]
Information
Introduction
Windows Command Shell (T1059.003) is a sub-technique within the MITRE ATT&CK framework under the Execution tactic. It involves adversaries leveraging the Windows command-line interface (cmd.exe) to execute commands, scripts, or binaries on a targeted system. Due to its availability by default on Windows operating systems, cmd.exe provides attackers a convenient and powerful tool to perform a wide range of malicious activities, including reconnaissance, execution of payloads, lateral movement, privilege escalation, and persistence.
Deep Dive Into Technique
The Windows command shell (cmd.exe) is a native command-line interpreter available on all Windows operating systems. Attackers use it primarily because of its ubiquity, flexibility, and ability to execute commands directly or through batch scripts (.bat or .cmd files).
Technical execution methods and mechanisms include:
Direct Command Execution:
Attackers execute commands directly via interactive shell or remotely through command-line interfaces such as PowerShell, WMI, or remote desktop sessions.
Example:
cmd.exe /c <malicious command>
Batch Scripts:
Attackers create batch files (.bat, .cmd) to automate malicious commands and scripts.
Batch scripts can perform complex operations, including file manipulation, service management, and registry modifications.
Obfuscation and Evasion:
Attackers frequently obfuscate commands through encoding, environment variables, or concatenation techniques to evade detection.
Example of environment variable obfuscation:
Use of command-line flags such as
/q(quiet mode),/c(carry out command), and/k(keep shell open) to control execution and visibility.
Execution via Remote Management Tools:
Attackers leverage remote execution methods such as PsExec, WMI, WinRM, or PowerShell Remoting to invoke cmd.exe remotely on compromised hosts.
Living-off-the-Land Binaries (LOLBins):
Legitimate Windows binaries (e.g., rundll32.exe, mshta.exe, regsvr32.exe) can invoke cmd.exe to execute malicious payloads indirectly.
When this Technique is Usually Used
Attack scenarios and stages where Windows Command Shell execution commonly appears include:
Initial Access and Execution:
Attackers exploiting vulnerabilities or phishing attacks may execute initial payloads through cmd.exe to establish a foothold.
Privilege Escalation:
Attackers leverage cmd.exe to execute commands that exploit vulnerabilities, misconfigurations, or weak permissions for privilege escalation.
Persistence:
Adversaries frequently use cmd.exe to set up persistent mechanisms, such as scheduled tasks, registry run keys, or startup folders.
Defense Evasion:
Attackers utilize cmd.exe to disable security tools, clear logs, or modify system configurations to evade detection.
Discovery and Reconnaissance:
Attackers execute built-in commands (e.g.,
net user,systeminfo,ipconfig,tasklist) to enumerate system information, users, network configurations, and running processes.
Lateral Movement:
Attackers utilize remote execution techniques through cmd.exe to move laterally within a compromised network environment.
Exfiltration:
Attackers use cmd.exe to compress, encrypt, or transfer sensitive information externally through built-in utilities (e.g.,
ftp,bitsadmin) or third-party tools.
How this Technique is Usually Detected
Detection methods, tools, and indicators of compromise (IoCs) include:
Process Creation and Command-Line Monitoring:
Monitor process creation events (Windows Event ID 4688) to detect suspicious cmd.exe executions.
Observe unusual command-line arguments, suspicious parent-child process relationships, or cmd.exe invoked by unexpected processes.
Sysmon and EDR Tools:
Utilize Sysinternals Sysmon or Endpoint Detection and Response (EDR) tools to capture detailed command-line execution logs.
Look for patterns indicative of obfuscation or suspicious command parameters.
Behavioral Analytics:
Employ security analytics solutions to detect anomalies in command-line executions, frequency, and context deviations from baseline user/system behavior.
Event Log Analysis:
Regularly analyze Windows Security Event Logs for unusual cmd.exe execution patterns, including unexpected user contexts or elevated privileges.
File System Monitoring:
Monitor creation and execution of batch (.bat/.cmd) files in unusual directories or with suspicious content.
Indicators of Compromise (IoCs):
Suspicious command-line parameters (e.g., encoded commands, obfuscation techniques).
Execution of commands commonly associated with reconnaissance or lateral movement (
net use,net user,ipconfig,tasklist,systeminfo).Abnormal parent-child process relationships (e.g., Office applications spawning cmd.exe).
Why it is Important to Detect This Technique
Detecting the malicious use of Windows Command Shell is critical due to its potential impacts on systems and networks:
Early Stage Detection:
Early identification of suspicious cmd.exe usage can disrupt attackers during initial access or execution phases, preventing further compromise.
Preventing Privilege Escalation:
Detection helps prevent attackers from escalating privileges to administrative levels, reducing potential damage.
Limiting Lateral Movement:
Timely detection can thwart attackers' attempts to move laterally across networks and limit the scope of compromise.
Reducing Data Exfiltration:
Early detection of suspicious command execution can prevent or limit data exfiltration attempts, protecting sensitive information.
Mitigating Persistence and Defense Evasion:
Identifying malicious cmd.exe usage can help defenders quickly remediate persistence mechanisms and defense evasion tactics, restoring system integrity.
Minimizing Operational Impact:
Early detection and response minimize downtime, reduce remediation costs, and protect organizational reputation.
Examples
Real-world examples demonstrating Windows Command Shell (T1059.003) usage include:
APT29 (Cozy Bear):
Used cmd.exe extensively for reconnaissance, lateral movement, and execution of payloads.
Leveraged obfuscated command-line arguments and batch files to evade detection and execute malicious scripts.
FIN7:
Utilized cmd.exe to execute reconnaissance commands such as
systeminfo,tasklist, andnet userto identify targets and escalate privileges.Employed batch scripts to automate lateral movement and persistence mechanisms.
Emotet Malware:
Leveraged cmd.exe to execute PowerShell commands, download additional payloads, and establish persistence mechanisms.
Frequently used obfuscation techniques to bypass traditional detection mechanisms.
TrickBot Malware:
Used cmd.exe to execute commands for lateral movement, reconnaissance, and credential harvesting.
Invoked cmd.exe through scheduled tasks and registry-based persistence methods.
Ryuk Ransomware:
Used cmd.exe to stop security services, delete backups, and disable recovery options prior to ransomware encryption.
Executed batch scripts to automate destructive operations and ensure maximum impact.
In each of these examples, attackers effectively leveraged cmd.exe due to its ubiquity, flexibility, and ease of use, highlighting the importance of robust detection and monitoring strategies.
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