Fnord - Designing Extractor For Obfuscated Code
Friday, September 20, 2019
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Title : Fnord - Designing Extractor For Obfuscated Code
link : Fnord - Designing Extractor For Obfuscated Code
Fnord is a designing extractor for obfuscated code
Description
Fnord has ii original functions:
1. Statistics
Fnord processes the file amongst a sliding window of varying size to extract all sequences of amongst a minimum length
Each business inward the tabular array contains:
2. YARA Rule Creation
Fnord also generates an experimental YARA rule. During YARA dominion creation it volition calculate a marking based inward the length of the sequence together with the release of occurrences (length * occurrences). It volition thus procedure each sequences past times removing all non-letter characters together with comparison them amongst a listing of keywords (case-insensitive) to give away sequences that are to a greater extent than interesting than others. Before writing each string to the dominion Fnord calculates a Levenshtein distance together with skips sequences that are equally good like to sequences that bring already been integrated inward the rule.
Status
[Experimental] Fnord was created a few days agone together with I bring tested it amongst a handful of samples. My approximate is that I'll arrange the defaults inward the coming weeks together with add together to a greater extent than or less to a greater extent than keywords, filters, scoring options.
Improve the Results
If you've flora obfuscated code inward a sample, utilization a hex editor to extract the obfuscated department of the sample together with salve to a novel file. Use that novel file for the analysis.
Play amongst the flags
Please post me samples that attain weak YARA rules that could locomote better.
Usage
Getting Started
Examples
Screenshots
FAQs
Why didn't yous integrate Fnord inward yarGen?
yarGen uses a white-listing approach to filter the strings that are best for the creation of a YARA rule. yarGen applies to a greater extent than or less regular expressions to arrange scores of strings earlier creating the YARA rules. But its approach is rattling dissimilar to the method used past times Fnord, which calculates the marking of the byte sequences based on statistics.
While yarGen is best used for un-obfuscated code. Fnord is for obfuscated code alone together with should attain much ameliorate results than yarGen.
Contact
Follow on Twitter for updates @cyb3rops
You are now reading the article Fnord - Designing Extractor For Obfuscated Code with the link address https://mederc.blogspot.com/2019/09/fnord-designing-extractor-for.html
Title : Fnord - Designing Extractor For Obfuscated Code
link : Fnord - Designing Extractor For Obfuscated Code
Fnord - Designing Extractor For Obfuscated Code
Fnord is a designing extractor for obfuscated code
Description
Fnord has ii original functions:
- Extract byte sequences together with exercise to a greater extent than or less statistics
- Use these statistics, combine length, release of occurrences, similarity together with keywords to exercise a YARA rule
1. Statistics
Fnord processes the file amongst a sliding window of varying size to extract all sequences of amongst a minimum length
-m X (default: 4) upwards to a maximum length -x X (default: 40). For each length, Fnord volition introduce the close ofttimes occurring sequences -t X (default: 3) inward a table.Each business inward the tabular array contains:
- Length
- Number of occurrences
- Sequence (string)
- Formatted (ascii/wide/hex)
- Hex encoded form
- Entropy
2. YARA Rule Creation
Fnord also generates an experimental YARA rule. During YARA dominion creation it volition calculate a marking based inward the length of the sequence together with the release of occurrences (length * occurrences). It volition thus procedure each sequences past times removing all non-letter characters together with comparison them amongst a listing of keywords (case-insensitive) to give away sequences that are to a greater extent than interesting than others. Before writing each string to the dominion Fnord calculates a Levenshtein distance together with skips sequences that are equally good like to sequences that bring already been integrated inward the rule.
Status
[Experimental] Fnord was created a few days agone together with I bring tested it amongst a handful of samples. My approximate is that I'll arrange the defaults inward the coming weeks together with add together to a greater extent than or less to a greater extent than keywords, filters, scoring options.
Improve the Results
If you've flora obfuscated code inward a sample, utilization a hex editor to extract the obfuscated department of the sample together with salve to a novel file. Use that novel file for the analysis.
Play amongst the flags
-s, -k, -r, --yara-strings, -mand-e`.Please post me samples that attain weak YARA rules that could locomote better.
Usage
____ __ / __/__ ___ _______/ / / _// _ \/ _ \/ __/ _ / /_/ /_//_/\___/_/ \_,_/ Pattern Extractor for Obfuscated Code v0.6, Florian Roth usage: fnord.py [-h] [-f file] [-m min] [-x max] [-t top] [-n min-occ] [-e min-entropy] [--strings] [--include-padding] [--debug] [--noyara] [-s similarity] [-k keywords-multiplier] [-r structure-multiplier] [-c count-limiter] [--yara-exact] [--yara-strings max] [--show-score] [--show-count] [--author author] Fnord - Pattern Extractor for Obfuscated Code optional arguments: -h, --help present this assist message together with teach out -f file File to procedure -m instant Minimum sequence length -x max Maximum sequence length -t locomote past times Number of items inward the Top x listing -n min-occ Minimum release of occurrences to present -e min-entropy Minimum entropy --strings Show strings alone --include-padding Include 0x00 together with 0x20 inward the extracted strings --debug Debug output YARA Rule Creation: --noyara Do non generate an experimental YARA dominion -s similarity Allowed similarity (use values betwixt 0.1=low together with 10=high, default=1.5) -k keywords-multiplier Keywords multiplier (multiplies marking of sequences if keyword is found) (best utilization values betwixt 1 together with 5, default=2.0) -r structure-multiplier Structure multiplier (multiplies marking of sequences if it is identified equally code construction together with non payload) (best utilization values betwixt 1 together with 5, default=2.0) -c count-limiter Count limiter (limts the acquit on of the count past times capping it at a for certain amount) (best utilization values betwixt v together with 100, default=20) --yara-exact Add magic header together with magic footer limitations to the dominion --yara-strings max Maximum sequence length --show-score Show marking inward comments of YARA rules --show-count Show count inward sample inward comments of YARA rules --author writer YARA dominion authorGetting Started
git clone https://github.com/Neo23x0/Fnord.gittogether withcd Fnordpip3 install -r ./requirements.txtpython3 ./fnord.py --help
Examples
python3 fnord.py -f ./test/wraeop.sct --yara-strings 10python3 fnord.py -f ./test/vbs.txt --show-score --show-count -t 1 -x 20python3 fnord.py -f ./test/inv-obf.txt --show-score --show-count -t 1 --yara-strings iv --yara-exactScreenshots
FAQs
Why didn't yous integrate Fnord inward yarGen?
yarGen uses a white-listing approach to filter the strings that are best for the creation of a YARA rule. yarGen applies to a greater extent than or less regular expressions to arrange scores of strings earlier creating the YARA rules. But its approach is rattling dissimilar to the method used past times Fnord, which calculates the marking of the byte sequences based on statistics.
While yarGen is best used for un-obfuscated code. Fnord is for obfuscated code alone together with should attain much ameliorate results than yarGen.
Contact
Follow on Twitter for updates @cyb3rops
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You are now reading the article Fnord - Designing Extractor For Obfuscated Code with the link address https://mederc.blogspot.com/2019/09/fnord-designing-extractor-for.html