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Example of Getting Analysts & Researchers Away, (Wed, Nov 16th)

2016-11-20 01:20

It is well-known that bad guys implement pieces of code to defeat security analysts and researchers. Modern malwareshave VM evasiontechniques to detect as soon as possible if they are executed in a sandboxenvironment. The same applies for web services like phishing pages or CC control panels.

Yesterday, I found a website delivering a malicious PE file. The URL was http://www.[redacted].com/king/prince.exe. This PE file was downloaded and executed by a malicious Office document. Nothing special here, its a classic attack scenario. Usually, when I receive aURL like this one, Im always trying to access the upper directory indexes and also some usual filenames / directories (I built and maintain my own dictionary for this purpose). Playing active-defense" />

The file zz.php is less interesting, its a simple PHP mailer. The dbl directory contains interesting pages that providea fake" />

In this case, attackers made another mistake, the source code of the phishing site was left on the server in the dbl.zip file. Once downloaded and analyzed, it revealed a classic attack trying to lure visitors and collect credentials. Note that the attacker was identified via his gmail.com address present in the scripts. But the most interesting file is called blocker.php"> ...include(blocker.php...

Lets have a look at this file. It performs several checks based on the visitors details (IP and browser).

First of all, it performs a reverse lookup of the visitor"> $hostname = gethostbyaddr($_SERVER[REMOTE_ADDR$blocked_words = array(above,google,softlayer,amazonaws,cyveillance,phishtank,dreamhost,netpilot,calyxinstitute,tor-exit, paypalforeach($blocked_words as $word) { if (substr_count($hostname, $word) 0) { header(HTTP/1.0 404 Not Found }}

Next, the visitorif(in_array($_SERVER[REMOTE_ADDR],$bannedIP)) { header(HTTP/1.0 404 Not Found} else { foreach($bannedIP as $ip) { if(preg_match(/ . $ip . /,$_SERVER[REMOTE_ADDR])){ header(HTTP/1.0 404 Not Found } }}

Here is the list of more relevant banned network:

  • Google
  • Digital Ocean
  • Cogent
  • Internet Systems Consortium
  • Amazon
  • Datapipe
  • DoD Network Information Center
  • Omnico"> if(strpos($_SERVER[HTTP_USER_AGENT], google) or strpos($_SERVER[HTTP_USER_AGENT], msnbot) or strpos($_SERVER[HTTP_USER_AGENT], Yahoo! Slurp) or strpos($_SERVER[HTTP_USER_AGENT], YahooSeeker) or strpos($_SERVER[HTTP_USER_AGENT], Googlebot) or strpos($_SERVER[HTTP_USER_AGENT], bingbot) or strpos($_SERVER[HTTP_USER_AGENT], crawler) or strpos($_SERVER[HTTP_USER_AGENT], PycURL) or strpos($_SERVER[HTTP_USER_AGENT], facebookexternalhit) !== false) { header(HTTP/1.0 404 Not Found }

    Surprisingly, this last"> Wget/1.13.4 (linux-gnu)curl/7.15.5 (x86_64-redhat-linux-gnu) libcurl/7.15.5 OpenSSL/0.9.8b zlib/1.2.3 libidn/0.6.5python-requests/2.9.1Python-urllib/2.7Java/1.8.0_111...

    Many ranges of IP addresses belongs to hosting companies. Many researchers use VPS and servers located there, thats why they are banned. In the same way, interesting targets for the phishing page are residential customers of the bank, connected via classic big ISPs.

    Conclusion: if you are hunting for malicious code / sites, use an anonymous IP address (a residential DSL line or cable is top) and be sure to use the right User-Agents to mimic classic targets.

    Xavier Mertens (@xme)
    ISC Handler - Freelance Security Consultant
    PGP Key

    (c) SANS Internet Storm Center. https://isc.sans.edu Creative Commons Attribution-Noncommercial 3.0 United States License.


    Source: ssr;pma&12712=diyrots?lmth.yraid/ude.snas.csi

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