Posté par: igor51 le mars 24, 2017, 14:00:30
On Jan. 27, we observed visitors to a Korean news site being
redirected to the GongDa Exploit Kit (EK), potentially exposing them
to malware infection. We will be referring to this site as KNS.
GongDa is an exploit kit that can compromise vulnerable endpoints by
use of exploits, allowing harmful malware to be installed on the
system. While GongDa is an older exploit kit that continues to use
Java exploits, it has also been found delivering both Flash and
VBScript exploits as well. Despite its shortcomings when compared to
newer EK’s such as Angler or Neutrino, GongDa proves that old tricks
(or vulnerabilities) can still work effectively.
ATTACK CHAIN
The attack chain is no different than previous GongDa attacks we’ve
seen in the past. A compromised page on the site loads a .js file that
redirects to the EK’s landing page.
Figure 1: GongDa EK attack chain
Where the initial page is at the first highlighted request shown in
Figure 1. The second request is the .js file jquery-1.3.2.min.js. It
has script code injected at the bottom that loads an iframe to
sekielec[.]co[.]kr/m/et/ad.html, the EK’s landing page as shown
in Figure 2.
Figure 2: Injected script in the .js leading to GongDa
We observed a number of KNS owned pages loading the malicious .js
redirecting to the GongDa landing page “/ad.html”.
From here, “ad.html” loaded:
sekielec.co.kr/m/et/swfobject.js
sekielec.co.kr/m/et/PnNxKk.html
sekielec.co.kr/m/et/jquery.js
EXPLOITS
GongDa has been observed serving the following CVE exploits in
recent attacks:
2011-3544, 2011-2140, 2012-0507, 2012-1723, 2012-1889,
2012-4681, 2012-5076, 2013-0422, 2013-0634 and 2014-6332.
In this particular attack, the landing page probes the target
machine and selects an exploit page to deliver to the victim. The
exploit page observed in this attack was
sekielec.co.kr/m/et/PnNxKk.html. It attempts to trigger
CVE-2014-6332, “Windows OLE Automation Array Remote Code Execution
Vulnerability”. This is a vulnerability that was patched by Microsoft
Security Bulletin
in November of 2014. It is a commonly used and dangerous vulnerability
that can give an attacker arbitrary command execution on a target system.
The exploit page begins by reversing a string of script code used to
start the exploitation process.
Figure 3 shows the before:
Figure 3: Reversed initiation code
And Figure 4 shows the after:
Figure 4: Initiation code
A call to the Create() function leads to a function call to
the trigger function Over(), which is shown in Figure 5.
Figure 5: Trigger function Over()
The Over() function is responsible for setting up conditions
and corrupting an OLE Automation array object, thus triggering the vulnerability.
Once the vulnerability is triggered, the attacker code can execute
commands on the system.
Three variables are assigned, as shown in Figure 6.
Figure 6: Command variables
The first variable (nburl) is a URL to the attacker malware.
The second variable (nbExE) is a randomly generated name for
the malware that is placed on the system. The third variable
(nbnurl) is simply the first variable enclosed in quotes.
nburl: http://smsforu.co.kr/RAD/stat/at.exe
Finally, the attacker code uses these variables and executes the
following commands, as shown in Figure 7.
Figure 7: Command beginning
The nbnurl and the nbExE variable are used in the
execution of the commands shown in Figure 8.
Figure 8: Command ending
The malicious file is placed in the “%SystemRoot%\system\” directory
using the nbExE variable described above as a filename.
PAYLOADS
During this GongDa attack we saw the payloads being served from a
domain within Korea:
smsforu[.]co[.]kr
With the following filename:
/rad/stat/at.exe
In recent GongDa attacks, we’ve observed payloads such as backdoors,
RATs, Trojans, and downloaders.
Some of the MD5’s observed include the following:
- aac178f775588ca1d42c00d4d95604bd
- 3d58f4b2008f6d87cab9166c09e513b5
- a18d1bce5618b23f592dae9133c25229
- 40be7c9424c6c6de0d560d358a020a5c
- 808e27fd120ade3ecfb2b21aeda8bc58
- ed751ce651d685100e00ed133e4e5018
ADDITIONAL INFO
Attacks involving the GongDa Exploit Kit are not new and are fairly
common in the APAC region. While it’s not the most cutting edge EK in
the wild, it is still effective because many systems in the region
seem to remain unpatched and defenseless against antiquated
vulnerabilities such as those used by GongDa.
Additionally, GongDa consistently leverages infrastructure hosted on
one of China’s largest ISP’s, China Telecom, operators of AS4134.
China Telecom hosts the domain 51yes[.]com, a web traffic statistics service.
One of GongDa’s telltale behaviors is the use of stat counters,
presumably for tracking the EK’s traffic and infection statistics. In
this case they most always come from countX[.]51yes[.]com,
based out of China. Figure 9 shows the GET requests for these stat counters.
Figure 9: Stat counter request
FireEye’s Dynamic Threat Intelligence shows that
count7[.]51yes[.].com has been used in multiple GongDa EK attacks in
January 2016 alone.
|
| valign="top"> |
| valign="top"> |
nstory.com/tmp/click/ad1.html nstory.com/vars/ad/ad1.html nstory.com/vars/cache/click/ad1.html |
odbike.co.kr/w3c/cdn/ad1.html odbike.co.kr/shop/skin/click/ad1.html odbike.co.kr/shop/temp/click/ad1.html odbike.co.kr/w3c/cdn/ad1.html |
poption.kr/gnu/cdn1/ad.html poption.kr/gnu/click/ad.html poption.kr/gnu/extend/ad/ad.html poption.kr/w3c/click/ad.html |
sekielec.co.kr/m/et/ad.html |
| valign="top"> |
| valign="top"> |
Checking other countX[.]51yes[.]com hits with GongDa
referrer’s, we saw hundreds of domains affected by the GongDa EK activity.
It is believed that the GongDa Exploit Kit has Chinese origins. The
hypothesis is derived from capabilities, usage, and the infrastructure
used to target various APAC region entities.
Interestingly, the registrant for the sekielec.co[.]kr GongDa
landing page domain, “rhhan AT sekihe.co[.]kr”, also registered a
number of other domains that have been observed as being GongDa
landing pages as well.
CONCLUSION
With a name reminiscent of a creature straight out of
Island, GongDa may not be the new kid on the block; however, as
demonstrated, it is still active and capable of wreaking havoc.
Network defenders in the APAC region should be aware of this EK and
take steps to ensure this “monster” never enters their network.
ACKNOWLEDGEMENTS
The authors and FireEye Labs would like to thank Dan Perez for his
contribution to this blog.
Source: GongDa vs. Korean News (http://)