1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
|
[](https://travis-ci.org/jvoisin/php-malware-finder)
# PHP Malware Finder
```
_______ __ __ _______
| ___ || |_| || |
| | | || || ___|
| |___| || || |___ Webshell finder,
| ___|| || ___| kiddies hunter,
| | | ||_|| || | website cleaner.
|___| |_| |_||___|
Detect potentially malicious PHP files.
```
## 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:
* [Bantam](https://github.com/gellin/bantam)
* [Best PHP Obfuscator]( http://www.pipsomania.com/best_php_obfuscator.do )
* [Carbylamine]( https://code.google.com/p/carbylamine/ )
* [Cipher Design]( http://cipherdesign.co.uk/service/php-obfuscator )
* [Cyklodev]( http://sysadmin.cyklodev.com/online-php-obfuscator/ )
* [Joes Web Tools Obfuscator]( http://www.joeswebtools.com/security/php-obfuscator/ )
* [P.A.S]( http://profexer.name/pas/download.php )
* [PHP Jiami]( http://www.phpjiami.com/ )
* [Php Obfuscator Encode]( http://w3webtools.com/encode-php-online/ )
* [SpinObf]( http://mohssen.org/SpinObf.php )
* [Weevely3]( https://github.com/epinna/weevely3 )
* [atomiku]( http://atomiku.com/online-php-code-obfuscator/ )
* [cobra obfuscator]( http://obfuscator.uk/example/ )
* [nano]( https://github.com/UltimateHackers/nano )
* [novahot]( https://github.com/chrisallenlane/novahot )
* [phpencode]( http://phpencode.org )
* [tennc]( http://tennc.github.io/webshell/ )
* [web-malware-collection]( https://github.com/nikicat/web-malware-collection )
* [webtoolsvn]( http://www.webtoolsvn.com/en-decode/ )
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 statement.
## How does it work?
Detection is performed by crawling the filesystem and testing files against a
[set](https://github.com/jvoisin/php-malware-finder/blob/master/php-malware-finder/php.yar)
of [YARA](http://virustotal.github.io/yara/) rules. Yes, it's that simple!
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, unzipped,
and then passed to some dangerous function like `system`".
## Installation
- [Install Yara](https://yara.readthedocs.io/en/stable/gettingstarted.html#compiling-and-installing-yara).
This is also possible via some Linux package managers:
- Debian: `sudo apt-get install yara`
- Red Hat: `yum install yara` (requires the [EPEL repository](https://fedoraproject.org/wiki/EPEL))
You can also compile it from source:
```
git clone git@github.com:VirusTotal/yara.git
cd yara/
YACC=bison ./configure
make
```
- Download php-malware-finder `git clone https://github.com/jvoisin/php-malware-finder.git`
## How to use it?
```
$ ./phpmalwarefinder -h
Usage phpmalwarefinder [-cfhtvl] <file|folder> ...
-c Optional path to a rule file
-f Fast mode
-h Show this help message
-t Specify the number of threads to use (8 by default)
-v Verbose mode
```
Or if you prefer to use `yara`:
```
$ yara -r ./php.yar /var/www
```
Please keep in mind that you should use at least YARA 3.4 because we're using
[hashes]( https://yara.readthedocs.org/en/latest/modules/hash.html ) 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.
Oh, and by the way, you can run the *comprehensive* testsuite with `make tests`.
## Whitelisting
Check the [whitelist.yar](https://github.com/jvoisin/php-malware-finder/blob/master/php-malware-finder/whitelist.yar) file.
If you're lazy, you can generate whitelists for entire folders with the
[generate_whitelist.py](https://github.com/jvoisin/php-malware-finder/blob/master/php-malware-finder/utils/generate_whitelist.py) script.
## Why should I use it instead of something else?
Because:
- It doesn't use [a single rule per sample](
https://github.com/Neo23x0/signature-base/blob/e264d66a8ea3be93db8482ab3d639a2ed3e9c949/yara/thor-webshells.yar
), since it only cares about finding malicious patterns, not specific webshells
- It has a [complete testsuite](https://travis-ci.org/jvoisin/php-malware-finder), to avoid regressions
- Its whitelist system doesn't rely on filenames
- It doesn't rely on (slow) [entropy computation]( https://en.wikipedia.org/wiki/Entropy_(information_theory) )
- It uses a ghetto-style static analysis, instead of relying on file hashes
- Thanks to the aforementioned pseudo-static analysis, it works (especially) well on obfuscated files
## Licensing
PHP-malware-finder is
[licensed](https://github.com/jvoisin/php-malware-finder/blob/master/php-malware-finder/LICENSE)
under the GNU Lesser 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.
|
