OllyDbg

OllyDbg is a 32-bit assembler level analyzing debugger software for Microsoft® Windows®. Emphasis on binary code analysis makes it particularly useful in cases where the source is unavailable. Olly Dbg is a shareware, but you can download and use it for free.

Features and Highlights

• An intuitive user interface, no cryptical commands
• Code analysis - traces registers, recognizes procedures, loops, API calls, switches, tables, constants, and strings
• Directly loads and debugs DLLs
• Object file scanning - locates routines from object files and libraries
• Allows for user-defined labels, comments and function descriptions
• Understands debugging information in Borland® format
• Saves patches between sessions, writes them back to executable file and updates fixups
• Open architecture - many third-party plugins are available
• No installation - no trash in registry or system directories
• Debugs multithread applications
• Attaches to running programs
• The configurable disassembler supports both MASM and IDEAL formats
• MMX, 3DNow! and SSE data types and instructions, including Athlon extensions
• Full UNICODE support
• Dynamically recognizes ASCII and UNICODE strings - also in Delphi format!
• Recognizes complex code constructs, like a call to jump to procedure
• Decodes call to more than 1900 standard API and 400 C functions
• Gives context-sensitive help on API functions from the external help file
• Sets conditional, logging, memory and hardware breakpoints
• Traces program execution, logs arguments of known functions
• Shows fixups
• Dynamically traces stack frames
• Searches for imprecise commands and masked binary sequences
• Searches whole allocated memory
• Finds references to constant or address range
• Examines and modifies memory, sets breakpoints and pauses program on-the-fly
• Assembles commands into the shortest binary form
• Starts from the floppy disk

To use OllyDbg, you need at least:

• 586/100 processor (586/300+ recommended)
• Microsoft Windows 95, Windows 98, Windows NT 4.0 (Service Pack 2 or higher), Windows 2000 or higher operational system
• 64 MB physical memory (128 MB recommended)
• At least 2 MB free disk space
• VGA display (SVGA with screen resolution at least 800x600 is strongly recommended)
• To debug programs on Windows NT or Windows 2000, you may have to have administrative rights.
• Mouse or compatible pointing device (required)