This is a cheat sheet of shortcuts and tips for analyzing and reverse-engineering malware. It covers the general malware analysis process, as well as useful tips for OllyDbg, IDA Pro, and other tools. Feel free to customize it to your own needs. The SANS malware analysis course FOR610 explores these, and other useful techniques. To print, use the one-sheet PDF version; you can also edit the Word version for you own needs. If you like this, take a look at my other IT cheat sheets.
- Set up a controlled, isolated laboratory in which to examine the malware specimen.
- Perform behavioral analysis to examine the specimen’s interactions with its environment.
- Perform static code analysis to further understand the specimen’s inner-workings.
- Perform dynamic code analysis to understand the more difficult aspects of the code.
- If necessary, unpack the specimen.
- Repeat steps 2, 3, and 4 (order may vary) until sufficient analysis objectives are met.
- Document findings and clean-up the laboratory for future analysis.
- Be ready to revert to good state via dd, VMware snapshots, CoreRestore, Ghost, SteadyState, etc.
- Monitor local (Process Monitor, Process Explorer) and network (Wireshark, tcpdump) interactions.
- Detect major local changes (RegShot, Autoruns).
- Redirect network traffic (hosts file, DNS, Honeyd).
- Activate services (IRC, HTTP, SMTP, etc.) as needed to evoke new behavior from the specimen.
IDA Pro for Static Code Analysis
|Show strings window||Shift+F12|
|Show operand as hex value||Q|
|Follow jump or call in view||Enter|
|Return to previous view||Esc|
|Go to next view||Ctrl+Enter|
|Show names window||Shift+F4|
|Display function’s flow chart||F12|
|Display graph of function calls||Ctrl+F12|
|Go to program’s entry point||Ctrl+E|
|Go to specific address||G|
|Rename a variable or function||N|
|Show listing of names||Ctrl+L|
|Display listing of segments||Ctrl+S|
|Show cross-references to selected function||Select function name » Ctrl+X|
|Show stack of current function||Ctrl+K|
OllyDbg for Dynamic Code Analysis
|Step into instruction||F7|
|Step over instruction||F8|
|Execute till next breakpoint||F9|
|Execute till next return||Ctrl+F9|
|Show previous executed instruction||–|
|Show next executed instruction||+|
|Return to previous view||*|
|Show memory map||Alt+M|
|Follow expression in view||Ctrl+G|
|Follow jump or call in view||Enter|
|Show listing of names||Ctrl+N|
|New binary search||Ctrl+B|
|Next binary search result||Ctrl+L|
|Show listing of software breakpoints||Alt+B|
|Assemble instruction in place of selected one||Select instruction » Spacebar|
|Edit data in memory or instruction opcode||Select data or instruction » Ctrl+E|
|Show SEH chain||View » SEH chain|
Bypassing Malware Defenses
- To try unpacking quickly, infect the system and dump from memory via LordPE or OllyDump.
- For more surgical unpacking, locate the Original Entry Point (OEP) after the unpacker executes.
- If cannot unpack cleanly, examine the packed specimen via dynamic code analysis while it runs.
- When unpacking in OllyDbg, try SFX (bytewise) and OllyDump’s “Find OEP by Section Hop”.
- Conceal OllyDbg via HideOD and OllyAdvanced.
- A JMP or CALL to EAX may indicate the OEP, possibly preceded by POPA or POPAD.
- Look out for tricky jumps via SEH, RET, CALL, etc.
- If the packer uses SEH, anticipate OEP by tracking stack areas used to store the packers’ handlers.
- Decode protected data by examining results of the decoding function via dynamic code analysis.
- Correct PE header problems with XPELister, LordPE, ImpREC, PEiD, etc.
- To get closer to OEP, try breaking on unpacker’s calls to LoadLibraryA or GetProcAddress.
Common x86 Registers and Uses
|EAX||Addition, multiplication, function results|
|EBP||Base for referencing function arguments (EBP+value) and local variables (EBP-value)|
|ESP||Points to the current “top” of the stack; changes via PUSH, POP, and others|
|EIP||Points to the next instruction|
|EFLAGS||Contains flags that store outcomes of computations (e.g., Zero and Carry flags)|
If you have suggestions for improving this cheat sheet, please let me know. Creative Commons v3 “Attribution” License for this Cheat Sheet v.1.6. Take a look at my other security cheat sheets.
Updated June 19, 2015