Tool written in python3 to determine where the AV signature is located in a binary/payload
Zip (with a password) your binary/payload caught by an AV so it won't be detected when placed in an environment protected by an AntiVirus. Launch the tool and specify the zip password and filename in the zip with the -p and -f options (infected/infected.bin by default)
This tool won't work for complex signatures
The tool will drop multiple files on the disk to determine on which pattern the signature is based on. It will obviously generate a lot of AV alerts, might be a good idea to run this on an host with no internet connection.
Once done, the result will be printed in stdout and a file (output.txt by default) containing the result will be generated.
If you know approximatly where your signature is located, you can specify one or more range in the payload to be analysed using the -r option. In the following example AVSignSeek will only try to find a signature in the following ranges:
./avsignseek.py zipfile.zip -r :0x100,0x150:0x1a0,0x1b0:
Automatically detects AV Signatures positional arguments: zip_file optional arguments: -h, --help show this help message and exit -s SLEEP waiting time between 2 tests (default: 20) -p ZIP_PASSWORD zip password (default: infected) -f FILENAME file name contained in the zip (default: infected.bin) -l LIMIT_SIGN signature limit (default: 64) -d TEST_DIR directory where testfiles will be placed (default: .) --subdiv SUBDIV subdiv per step (default: 4) -o OUTPUT_FILE output_file (default: output.txt) -r RANGES_STR range (default: ":") -b REPLACING_VALUE character or byte used as a replacing value (default: "0x00") --manual wait for a manual input instead of a specific time (default: false)
Reflective DLL caught by Kaspersky AV, the signature based on the exported dll function name "ReflectiveLoader"
=== AVSignSeek === [+] Signature between bytes 88220 and 88284 [+] Bytes: 4d 61 6c 77 61 72 65 54 65 73 74 2e 64 6c 6c 00 MalwareTest.dll. 52 65 66 6c 65 63 74 69 76 65 4c 6f 61 64 65 72 ReflectiveLoader 00 66 75 6e 63 5f 74 65 73 74 00 00 00 00 00 00 .func_test...... 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ [+] Strings: > MalwareTest.dll > ReflectiveLoader > func_test
False Positives due to binary header
While trying to locate the AV signature, the AVSignSeek might break a header or another way used by the AV to determine the file type, and the AV won't detect the file as malicious anymore, resulting in a false positive. It can be prevented by using the start byte and end byte option (-s and -e) to remove the "header" from the analysis
Unable to locate the signature
If there is multiple signature in a single payload, AVSignSeek won't be able to locate them
- Multiple signature detection
- PE-specific signature detection (it will detect in which section/exported function/... the signature is located)