VDSO Hijacking

VDSO Hijacking [T1055.014]

Information

• Name: VDSO Hijacking

• ID: T1055.014

• Tactics: TA0005, TA0004

• Technique: T1055

Introduction

VDSO Hijacking (T1055.014) is a sub-technique under the MITRE ATT&CK framework's "Process Injection" (T1055) technique. It involves manipulating the Virtual Dynamic Shared Object (VDSO) mechanism in Linux systems to execute malicious code. The VDSO is a shared library mapped into the memory space of processes by the Linux kernel to accelerate certain system calls. Attackers exploit this by overwriting or redirecting function pointers within the VDSO memory region, allowing them to execute arbitrary code within the context of legitimate processes. This technique enables attackers to evade detection, elevate privileges, and maintain persistence.

Deep Dive Into Technique

The Virtual Dynamic Shared Object (VDSO) is a small shared library automatically mapped into the address space of user-space processes by the Linux kernel. Its primary purpose is to facilitate efficient system call execution by avoiding kernel context switches for certain frequently used system calls, such as gettimeofday(), clock_gettime(), and getcpu().

Attackers exploit this mechanism by performing the following steps:

1. Identifying Target Process:

   • Attackers select a running process that has the VDSO mapped into its memory space. Typically, this is a widely used or trusted process to avoid suspicion.

2. Memory Access and Injection:

   • The attacker gains sufficient privileges or exploits vulnerabilities allowing them to access the memory space of the targeted process.

   • Using techniques such as ptrace(), they inject malicious shellcode or overwrite function pointers in the VDSO region.

3. Hijacking Execution Flow:

   • Attackers redirect legitimate function calls within the VDSO to their injected malicious code.

   • When the compromised process attempts to execute a legitimate system call via the VDSO, it inadvertently executes attacker-controlled payloads.

4. Privilege Escalation and Persistence:

   • By injecting code into a trusted process, attackers can escalate privileges, execute commands with higher permissions, or maintain persistent presence in the compromised system.

Technical characteristics of VDSO Hijacking include:

• Manipulation of memory mappings (/proc/[pid]/maps) to identify VDSO location.

• Use of debugging or tracing utilities (ptrace(), gdb) to inject code into the target process.

• Overwriting function pointers or instruction sequences within the VDSO memory region.

• Leveraging kernel vulnerabilities or misconfigurations to gain initial access or escalate privileges.

When this Technique is Usually Used

VDSO Hijacking typically appears in the following attack scenarios and stages:

• Privilege Escalation:

  • Attackers leverage VDSO hijacking to escalate privileges by injecting malicious payloads into processes running with elevated permissions.

• Persistence:

  • Attackers may use this technique to maintain persistent access by embedding malicious code within legitimate processes, thereby evading detection and surviving system reboots.

• Defense Evasion:

  • Manipulating VDSO allows attackers to execute code within trusted processes, making detection more challenging for security solutions.

• Credential Access and Data Exfiltration:

  • Injected code may target sensitive data extraction, credential harvesting, or command execution within the context of privileged processes.

• Advanced Persistent Threat (APT) Campaigns:

  • Sophisticated threat actors commonly utilize VDSO hijacking to maintain stealthy, long-term access to targeted networks.

How this Technique is Usually Detected

Detection of VDSO Hijacking involves multiple methods, tools, and indicators of compromise (IoCs):

• Memory Monitoring and Integrity Checks:

  • Monitor memory regions of critical processes for unexpected changes, especially within the VDSO mapped region.

  • Tools such as Volatility Framework, Rekall, or custom memory forensic scripts can inspect memory dumps for anomalies.

• Behavioral Analysis:

  • Identify abnormal behaviors in trusted processes, such as unusual system calls, unexpected network connections, or anomalous resource usage.

• Endpoint Detection and Response (EDR) Tools:

  • Modern EDR solutions can detect suspicious memory injections and alterations within processes, triggering alerts for further investigation.

• System Call Tracing and Auditing:

  • Enable Linux audit frameworks (auditd) and tracing utilities (strace, ltrace) to monitor suspicious process interactions and anomalous function calls.

• Indicators of Compromise (IoCs):

  • Unusual entries or modifications in /proc/[pid]/maps indicating unexpected memory mappings.

  • Presence of debugging or tracing tools (ptrace usage) in logs associated with critical processes.

  • Unexpected process crashes or segmentation faults due to corrupted VDSO functions.

Why it is Important to Detect This Technique

Early detection of VDSO Hijacking is crucial due to the following potential impacts:

• Privilege Escalation:

  • Attackers can escalate privileges by injecting malicious code into elevated processes, gaining administrative control over the system.

• Evasion of Security Controls:

  • Injected malicious code within legitimate processes can bypass traditional security mechanisms, antivirus software, and endpoint protection solutions.

• Persistence and Long-Term Compromise:

  • Hijacking trusted processes through VDSO manipulation allows attackers to maintain persistent access, facilitating prolonged espionage, data theft, or sabotage.

• Data Exfiltration and Credential Theft:

  • Attackers may leverage compromised processes to access sensitive data, credentials, and proprietary information, posing significant risks to organizational security.

• Damage to System Stability:

  • Unauthorized modifications to critical system functions can lead to instability, crashes, or unintended behaviors, impacting service availability and reliability.

Early identification and response to this technique can significantly reduce the risk of severe damage, loss of sensitive information, and prolonged intrusion.

Examples

Real-world examples of VDSO Hijacking include:

• Linux Malware and Rootkits:

  • Advanced Linux rootkits such as "Diamorphine" and "Reptile" have incorporated VDSO manipulation techniques to hide their presence and evade detection.

  • These rootkits inject malicious payloads into the VDSO region, allowing stealthy execution of commands and hiding malicious activities from monitoring tools.

• APT Campaigns and Nation-State Actors:

  • Advanced Persistent Threat groups have been observed employing VDSO Hijacking to achieve stealthy persistence and privilege escalation on Linux-based servers and infrastructure.

  • This technique allows attackers to maintain long-term access while minimizing detection by security teams, thus enabling espionage and data exfiltration.

• Publicly Documented Proof-of-Concept (PoC) Exploits:

  • Security researchers have demonstrated proof-of-concept exploits leveraging VDSO Hijacking to illustrate vulnerabilities and raise awareness about potential misuse.

  • Publicly available PoC code has been shared through platforms such as GitHub, highlighting the practical risks associated with this technique.

• Incident Response Cases:

  • Security incident reports and forensic analyses have documented instances where attackers leveraged VDSO Hijacking to escalate privileges and evade detection within compromised Linux environments.

  • Incident responders have identified VDSO manipulation through memory forensic analysis, tracing injected code back to attacker-controlled payloads.

These examples illustrate the practical use of VDSO Hijacking in real-world attacks, emphasizing the importance of comprehensive monitoring, detection, and mitigation strategies.