Tuesday, June 26, 2012

Cleartrip.com Infected with Blackhole Exploit Kit.


Cleartrip is used for booking flights, hotels and IRCTC Indian Railways tickets  in India. It is a leading online booking portal. Recently, I was searching flight information on www.cleartrip.com and my desktop antivirus delivered the following  alert:

Infection alert of AVG antivirus.

AVG had detected a Blackhole exploit on the following page:
hxxp://www.cleartrip.com/eadserver/delivery/afr.php?zoneid=43&target=_blank&cb=0.027297518110020458
Let’s take a look at a wireshark capture taken while visiting the page.

Packet capture snapshot of cleartrip.com


The page content of "hxxp://www.cleartrip.com/eadserver/delivery/afr.php?zoneid=43&target=_blank&cb=0.027297518110020458" was broken, but after a bit of searching on the site, I was able to ultimately find the same malicious code with intact de-obfuscation logic.

The URL identified this time was:
hxxp://www.cleartrip.com/eadserver/delivery/afr.php?zoneid=43&target=_blank&cb=0.46843633663340656.

For further analysis, we’ll take a look at page content. A snippet of the code is shown below:


Code source of blocked page

Much of the content is obfuscated, so we’ll need to first de-obfuscate it in order to analyze it further.
Let’s look the obfuscated code delivered this time:


Obfuscated code souce.

De-obfuscation of the aforementioned code reveals JavaScript which was creates a 1x1 pixel iFrame pointing to  “hxxp://trafficgoodster.info/banners.cgi?advert_id=1&banner_id=1&chid=341aa8fca26bcff7830499c1c5f8e359”
The de-obfuscated code is shown below.

URL in iFrame tag

Fortunately, Google has blacklisted that particular URL.
Let’s take look at source of the page:

Source page view.
This URL displays a .gif file, but if you look carefully, you will see that an iFrame is also delivered. It is this URL (highlighted above), which points to the Blackhole Exploit Kit.
The .info domain used in the iframe is registered for one year and was registered only recently. Naturally, newly registered domains tend to have higher risk as they attackers often register new names for a single attack. Let’s do a whois query on the domain:
Domain Name: TRAFFICGOODSTER.INFO
Created On: 14-Jun-2012 07:52:31 UTC
Last Updated On: 14-Jun-2012 07:52:31 UTC
Expiration Date: 14-Jun-2013 07:52:31 UTC
Spammers also prefer .info domains as they as less expensive to register than .com or .net domain names.
A de-obfuscated version of the contents is shown below:


A De-obfuscated contents.
 
Zscaler has informed cleartrip.com on this infection.

I thank to my colleague Pradeep Kulkarni for helping to analyze this infection.

8 comments:

Palani said...

Good work.

ketan mujumdar said...

Wonder re :D ... too good .. !!!

ketan mujumdar said...

Wonder !!! good one :)

sukalp said...

Nice work.. Keep going..

vbmade2000 said...

Very informative and helpful content.

vbmade2000 said...

Very informative and helpful content.

Thanks for sharing.

Sandeep said...

so how does the vulnerability affect visitors of the site... what does the blackhole exploit kit do ?
thanks

Julien Sobrier said...

@Sandeep We did a detailed analysis of the Blackhole Exploit kit in February: http://research.zscaler.com/2012/02/analysis-of-blackhole-exploit-page.html