OllyDbg

OllyDbg is a 32-bit assembler level analysing debugger for Microsoft® Windows®. Emphasis on binary code analysis makes it particularly useful in cases where source is unavailable. OllyDbg is a shareware, but you can download and use it for free. Special highlights are: 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 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 call to jump to procedure Decodes calls to more than 1900 standard API and 400 C functions Gives context-sensitive help on API functions from 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 and much, much more!