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

Luke404 asked:

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)?

My answer:

In addition to ClamAV, consider using 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.

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