This cheat sheet presents tips for analyzing and reverse-engineering malware. It outlines the steps for performing behavioral and code-level analysis of malicious software.
Overview of the Malware Analysis Process
- Use automated analysis sandbox tools for an initial assessment of the suspicious file.
- Set up a controlled, isolated laboratory in which to examine the malware specimen.
- Examine static properties and meta-data of the specimen for triage and early theories.
- Perform behavioural 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.
- Perform memory forensics of the infected lab system to supplement the other findings.
- Repeat steps 4-8 above as necessary (the order may vary) until analysis objectives are met.
- Document findings, save analysis artifacts and clean-up the laboratory for future analysis.
- Be ready to revert to good state via virtualization snapshots, Clonezilla, dd, FOG, PXE booting, etc.
- Monitor local interactions (Process Explorer, Process Monitor, ProcDOT, Noriben).
- Detect major local changes (RegShot, Autoruns).
- Monitor network interactions (Wireshark, Fiddler).
- Redirect network traffic (fakedns, FakeNet-NG).
- Activate services (INetSim or actual services) requested by malware and reinfect the system.
- Adjust the runtime environment for the specimen as it requests additional local or network resources.
Ghidra for Static Code Analysis
|Go to specific testination||g|
|Show references to selected instruction||Ctrl+Shift+f|
|Insert a comment||;|
|Follow jump or call||Enter|
|Return to previous location||Alt+Left|
|Go to next view||Alt+Right|
|Define data type||t|
|Add a bookmark||Ctrl+d|
|Add or edit a label||l|
|Disassemble selected values||d|
x64dbg/x32dbg for Dynamic Code Analysis
|Run the code||F9|
|Step into/over instruction||F7 / F8|
|Execute until selected instruction||F4|
|Execute untill next return||Ctrl+F9|
|Show previous/next executed instruction||– / +|
|Return to previous view||*|
|Go to specific expression||Ctrl+g|
|Insert comment/label||; / :|
|Show current function as a graph||g|
|Find specific pattern||Ctrl+b|
|Set software breakpoint on specific instruction||Select instruction » F2|
|Set software breakpoint on API||Go to Command prompt » SetBPX API Name|
|Highlight all occurrences of the keyword in disassembler||h » Click on keyword|
|Assemble instruction in place of selected one||Select instruction » Spacebar|
|Edit data in memory or instruction opcode||Select data or instruction » Ctrl+e|
|Extract API call references||Right-click in disassembler » Search for » Current module » Intermodular calls|
Unpacking Malicious Code
- Determine whether the specimen is packed by using Detect It Easy, Exeinfo PE, Bytehist, peframe, etc.
- To try unpacking the specimen quickly, infect the lab system and dump from memory using Scylla.
- For more precision, find the Original Entry Point (OEP) in a debugger and dump with OllyDumpEx.
- To find the OEP, anticipate the condition close to the end of the unpacker and set the breakpoint.
- Try setting a memory breakpoint on the stack in the unpacker’s beginning to catch it during cleanup.
- To get closer to the OEP, set breakpoints on APIs such as LoadLibrary, VirtualAlloc, etc.
- To intercept process injection set breakpoints on VirtualAllocEx, WriteProcessMemory, etc.
- If cannot dump cleanly, examine the packed specimen via dynamic code analysis while it runs.
- Rebuild imports and other aspects of the dumped file using Scylla, Imports Fixer, UIF, pe_unmapper.
Bypassing Other Analysis Defenses
- Decode obfuscated strings statically using FLARE, xorsearch, Balbuzard, etc.
- Decode data in a debugger by setting a breakpoint after the decoding function and examining results.
- Conceal x64dbg/x32dbg via the ScyllaHide plugin.
- To disable anti-analysis functionality, locate and patch the defensive code using a debugger.
- Look out for tricky jumps via TLS, SEH, RET, CALL, etc. when stepping through the code in a debugger.
- If analyzing shellcode, use scdbg and jmp2it.
- Disable ASLR via setdllcharacteristics, CFF Explorer.
credits: L Zeltser
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