Disassembly: Dll

Understanding these differences is critical because disassembly tools must parse the header differently. 3. Methodology for DLL Disassembly 3.1 Static Disassembly (Offline Analysis) Static analysis examines the DLL file without executing it.

Disassembly is the process of translating binary machine code into symbolic assembly language. For DLLs, this involves reconstructing logic without a predefined execution start point. 2. Architectural Differences: DLL vs. EXE | Feature | EXE | DLL | | :--- | :--- | :--- | | Entry Point | WinMain or main | DllMain (called on attach/detach) | | Base Address | Fixed (e.g., 0x400000 ) | Relocatable (ASLR preferred) | | Export Table | Optional (for resources) | Mandatory (exposed functions) | | Execution | Standalone | Hosted by a process (e.g., rundll32.exe ) | disassembly dll

Author: AI Research Division Date: April 14, 2026 Abstract Dynamic Link Libraries (DLLs) are fundamental to the Windows operating system, promoting code reuse and modularity. However, from a security research and malware analysis perspective, DLLs are black boxes containing executable logic. This paper explores the technical process of disassembling DLLs—converting machine code back into human-readable assembly language. We examine the structural differences between DLLs and standard executables (EXEs), the tooling required (IDA Pro, Ghidra, x64dbg), and the specific challenges posed by position-independent code, relocations, and export tables. 1. Introduction A DLL is a library of functions and resources that can be called by multiple applications simultaneously. Unlike a standard EXE, a DLL cannot be executed directly (it lacks an entry point like WinMain ). To analyze a DLL’s behavior—whether for vulnerability research, malware analysis, or legacy software maintenance—an analyst must disassemble it. Disassembly is the process of translating binary machine

__declspec(dllexport) int Add(int a, int b) return a + b; Architectural Differences: DLL vs

rundll32.exe target.dll, ExportedFunctionName 4.1 Position-Independent Code (PIC) DLLs use relative addressing because their base address changes due to ASLR (Address Space Layout Randomization). Disassemblers must correctly interpret RIP-relative addressing (x64) or rely on relocation tables. 4.2 No Single Entry Point Unlike an EXE, a DLL has many entry points (its exports). The analyst must manually determine which function is relevant, as DllMain often just returns TRUE . 4.3 Obfuscation & Packing Malicious DLLs are often packed (e.g., with UPX, Themida). The disassembler sees a tiny stub that unpacks the real DLL in memory. Solution: Use a unpacker or dump the process memory after unpacking. 4.4 Import Address Table (IAT) Fixups DLLs call functions from other DLLs (e.g., kernel32.dll ). During disassembly, these calls appear as jumps to placeholder addresses. A good disassembler automatically resolves these via the IAT. 5. Practical Case Study: Disassembling a Simple DLL Source (C):