local - Is there a static, server-side vulnerability/virus/malware/BadThings™ scanner?

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We run a shared hosting webserver with
the usual LAMP stack. It is up and running since many years ago (uhm, Apache-1.3 and
PHP-3 days?) and went through many iterations. We strive to have good sysadmin policies,
like keeping all the stack up-to-date, checking for weak passwords, minimizing the
attack surface, using suhosin, keeping an eye on systems logs, and so on. Of course
every virtual host is confined to its directory (both for FTP access and as php
open_basedir).

But at the end of the
day it's always a webserver running untrusted PHP crap uploaded by customers (read:
unknown and mostly-stupid users without any IT experience) with HTTP exposed to the
world (web forms and whatnot)... these scenarios are not too
uncommon:

• user gives its
  password to too many people and its site gets
  compromised


• user's PC gets compromised and the FTP / web
  app / whatever password stolen from there


• user installs
  crappy PHP stuff and it gets compromised


• user installs
  good PHP stuff (does it even exists?) but doesn't update in years and it gets
  compromised


• user writes its own PHP stuff
  (ARGH! they're coming outta the ----------
  walls!)


• and so on. you got the
  idea.

When
investigating compromised PHP/JS/HTML/whatever stuff we sometimes find malware in the
form of javascript (either in .js files or embedded in html stuff) and sometimes we even
find .zip files with malware/viruses for Microsoft Windows
inside.

With such a wild environment it is not
possible to repeatedly run automated vulnerability tests on the web sites, and probably
it wouldn't be much useful either. I'm also thinking stuff like mod_security would be
out of question in such a shared, generic, out of control
environment.

But I'm wondering if there is
anything antivirus-like that we could run server-side, at least to look for web sites
compromised with well known javascript or executable stuff, or known vulnerabilities in
old versions of PHP web apps. Something to run from cron every night and get a nice
email report.

Is there such a thing? Could
clamav detect some of those nasty JS stuff? (I'm assuming we can already use it to
detect uploaded zip files with Win32 malware)
Anything else I hadn't thought
of that could be run server-side for a static scan?
And what about content
stored in MySQL (eg. javascript uploaded from forms and stored in SQL for later display
on web pages)?

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class="normal">Answer

In
addition to ClamAV, consider using href="http://www.rfxn.com/projects/linux-malware-detect/" rel="nofollow
noreferrer">Maldet for additional malware detection. According to the docs,
it has the ability to integrate with ClamAV, though I haven't personally set this
up.