What does it detect?
PHP-malware-finder does its very best to detect obfuscated/dodgy code as well as files using PHP functions often used in malwares/webshells.
The following list of encoders/obfuscators/webshells are also detected:
- Best PHP Obfuscator
- Cipher Design
- Joes Web Tools Obfuscator
- Php Obfuscator Encode
- cobra obfuscator
Of course it’s trivial to bypass PMF, but its goal is to catch kiddies and idiots, not people with a working brain.
If you report a stupid tailored bypass for PMF, you likely belong to one (or both) category, and should re-read the previous sentence.
Instead of using an hash-based approach, PMF tries as much as possible to use semantic patterns, to detect things like “a
$_GET variable is decoded two times, unziped, and then passed to some dangerous function like
$ ./phpmalwarefinder -h Usage phpmalwarefinder [-cfhtv] [-l (php|asp)] <file|folder> ... -c Optional path to a configuration file -f Fast mode -h Show this help message -t Specify the number of threads to use (8 by default) -v Verbose mode -l Set language ('asp', 'php')
Or if you prefer to use
$ yara -r ./php.yar /var/www $ yara -r ./asp.yar /var/www
Please keep in mind that you should use at least YARA 3.4 because we’re using hashes for the whitelist system, and greedy regexps. Please note that if you plan to build yara from sources, libssl-dev must be installed on your system in order to have support for hashes.
Ho, and by the way, you can run the comprehensive testsuite with
- It doesn’t use a single rule per sample, since it only cares about finding malicious patterns, not specific webshells
- Its whitelist system doesn’t rely on filenames
- It doesn’t rely on (slow) entropy calculation
- It uses a ghetto-style static analysis, instead of relying on file hashes
- Thanks to the aforementioned pseudo-static analysis, it works on obfuscated files too
PHP-malware-finder is licensed under the GNU General Public License v3.
The amazing YARA project is licensed under the Apache v2.0 license.
Patches, whitelists or samples are of course more than welcome.