Add files via upload

Finds PHP content in files w/ image headers (JPG/GIF/PNG) via magic numbers.

Webshells/WShell_PHP_in_images.yar

+/*
+    Finds PHP code in JP(E)Gs, GIFs, PNGs.
+    Magic numbers via Wikipedia.
+*/
+rule php_in_image
+{
+    meta:
+        author      = "Vlad https://github.com/vlad-s"
+        date        = "2016/07/18"
+        description = "Finds image files w/ PHP code in images"
+    strings:
+        $gif = /^GIF8[79]a/
+        $jfif = { ff d8 ff ee 00 10 4a 46 49 }
+        $png = { 89 50 4e 47 0d 0a 1a 0a }
+
+        $php_tag = "<?php"
+    condition:
+        (($gif at 0) or
+        ($jfif at 0) or
+        ($png at 0)) and
+
+        $php_tag
+}