What is SEH (Structured Exception Handling) overwrite?

The Dangers of SEH Overwrite: Understanding Structured Exception Handling Vulnerabilities in Computer Security and AntiVirus Software

Structured Exception Handling (SEH) is a mechanism built into Microsoft Windows operating systems to manage exceptions - anomalies or extraordinary conditions that require particular management. These exceptions may arise from either software or hardware conditions. For application developers, SEH provides a controlled technique for managing errors or exceptional conditions during program execution; it brings about a structured, uniform method to declaring handlers that can respond to exceptions.

However SEH also has a record of being misused by attackers to circumvent precautions and security measures. One method of bypassing detections and exploiting vulnerabilities is known as a Structured Exception Handling overwrite, colloquially known as the 'SEH Overwrite Attack.'

In an SEH overwrite attack, the cyberattacker aims to overwrite both the exception handler and a next-level pointer in a process' SEH chain. An attacker can take control of the application's execution when a software exception is thrown if this occurs. This attack technique is often used to inject and operate malicious code without having the required security privileges.

The primary difficulty related to such attacks is regarding Overwrite protections. Defensive mechanisms such as Data Execution Prevention (DEP) and Address Space Layout Randomization (ASLR) are typically employed in modern operating systems or computer processing units to avoid such attacks.

DEP is a security precaution intended to stop damaging programs from executing code from any data storage in memory. This mechanism designates areas of memory as either executable or non-executable; hence, even if an SEH overwrite injection is successful, the malicious executable codes cannot execute in non-executable areas because of DEP.

Despite such measures, clever attackers can still bypass such protections, leaving software vulnerable to exploitation via techniques such as Return-Oriented Programming (ROP). It involves an attacker injecting sequences of instructions, deployable on existing programs, each ending with a return instruction. Combined, they can perform malicious operations bypassing DEP protections without ever needing to mark memory segments as executable.

Anti-virus software plays a crucial role in safeguarding against such cyberattacks, including SEH overwrite attacks. High end and up-to-date antivirus systems deploy heuristic analysis, which offers potent protection against SEH overwrite attempts. In heuristic analysis, the antivirus scans the behavior of programs, studying patterns to detect anything unprecedented or suspicious. If it additionally encounters uncommon SEH alterations or suspects an SEH overwrite incident, the antivirus will alert the user and stop the notation or process, minimizing the chance of an exploit.

Employing robust improvements in software engineering practices to keep away exploitable vulnerabilities is also very beneficial. Precisely, the use of secure software development methodologies which incorporate defense strategies can aid in escape from scenarios that can prompt SEH overwrite attacks.

To sum up, especially with increasing cyber threats and ingenious attack modes, understanding and safeguarding environments from SEH overwrite attacks remains a cornerstone in the colossal field of cybersecurity. A mix of preventive shields (such as DEP and ASLR), mitigative mechanisms (like antivirus software equipped with heuristic analysis), and improved, secure coding practices can serve as a broad bulwark against attackers aiming to performing SEH overwrite exploit.

SEH (Structured Exception Handling) overwrite FAQs