Information Security News
An actor using gates registered through BizCN recently switched from Fiesta to Nuclear exploit kit (EK). This happened around last month, and we first noticed the change on 2015-06-15.
I started writing about this actor in 2014 [1, 2] and recently posted an ISC diary about it on 2015-04-28 . Ive been calling this group the BizCN gate actor because domains used for the gate have all been registered through the Chinese registrar BizCN.
We collected traffic and malware samples related to this actor from Friday 2015-07-03 through Sunday 2015-07-05. This traffic has the following characteristics:
NOTE: For now, Kovter is relatively easy to spot, since its the only malware Ive noticed that updates the infected hosts Flash player .
Chain of events
Lets take a closer look at how this happens.
Compromised websites are the first step in an infection chain." />
BizCN-registered gate domain
Weve found at least four IP addresses hosting the BizCN-registered gate domain. They are:
If you have proxy logs or other records of your HTTP traffic, search for these IP addresses. If you find the referrers, you might discover other websites compromised by this actor.
Examples of infection traffic generated from 2015-07-03 through 2015-07-05 all show 188.8.131.52 as the IP address hosting Nuclear EK. This IP address is registered to Vultr, a hosting provider specializing in SSD cloud servers . " />
Finally, Nuclear EK sends the malware payload. It" />
Malware sent by this actor
During the three-day period, we infected ten hosts, saw two different Flash exploits, and retrieved five different malware payloads. Most of these payloads were Kovter (ad fraud malware)." />
Below are links to reports from hybrid-analysis.com for the individual pieces of malware:
Its usually difficult to generate a full chain of infection traffic from compromised websites associated with this BizCN gate actor. We often see HTTP GET requests to the gate domain return a 404 Not Found. In some cases, the gate domain might not appear in traffic at all.
We believe the BizCN gate actor will continue to make changes as a way to evade detection. Fortunately, the ISC and other organizations try our best to track these actors, and well let you know if we discover any significant changes.
Examples of the traffic and malware can be found at:
As always, the zip file is password-protected with the standard password. If you dont know it, email [email protected] and ask.
Last week I received another malicious document with embedded payload encoded with base64. A bit tired of repeating the same manual operations to extract and decode base64 content, I quickly wrote a small Python script to help me. base64dump.py searches through the given file for base64 strings (delimited by non-base64 characters), and produce a report like this one:
Here is a video of the tool in action.