by Brendan Griffin and Gary Warner
Today Malcovery’s analysts identified a new trojan based heavily on the GameOver Zeus binary. It was distributed as the attachment to three spam email templates, utilizing the simplest method of infection through which this trojan is deployed.
From 9:06 AM to 9:55 AM we saw spam messages claiming to be from NatWest
From 9:34 AM to 10:50 AM we saw spam messages with the subject “Essentra PastDue” like these:
The longest lasting of the spam campaigns was imitating M&T Bank, with a subject of “E100 MTB ACH Monitor Event Notification. That campaign is still ongoing as of this writing.
The three spam campaigns each had a .zip attachment. Each of these contained the same file in the form of a “.scr” file with the hash:
At this timestamp (1600 Central time, 7 hours after we first noticed the spam campaign) the detection rate at VirusTotal is 10/54:
Once the attachment was opened and the malware payload executed, the malware began to make attempts to contact certain websites in accordance with a domain generation algorithm. The goal of these contact attempts is to make contact with a server that can in turn provide instructions to the malware. Many sandboxes would have failed to launch the malware, as the presence of VMWare Tools will stop the malware from executing. Other sandboxes would not have noticed the successful connection, because the malware took between 6 and 10 minutes to randomly generate the single domain name that was used successfully to launch the new Zeus trojan and download the bank information “webinject” files from the server.
The Domain Generation Algorithm is a method for a criminal to regain access to his botnet. Based on the current date, random-looking domain names are calculated and the malware reaches out via the Internet to see if that domain exists.
Malcovery analysts confirmed with the FBI and Dell Secure Works that the original GameOver Zeus is still "locked down". This new DGA list is not related to the original GameOver Zeus but bears a striking resemblance to the DGA utilized by that trojan. In addition to a new DGA, the malware seems to have traded its Peer to Peer Infrastructure for a new Fast Flux hosted C&C strategy.
The successful domain: cfs50p1je5ljdfs3p7n17odtuw.biz was registered this morning in China with the registrar “TodayNIC.com”:
Domain Name: CFS50P1JE5LJDFS3P7N17ODTUW.BIZ
Domain ID: D61087891-BIZ
Sponsoring Registrar: TODAYNIC.COM, INC.
Sponsoring Registrar IANA ID: 697
Registrar URL (registration services): www.todaynic.biz
Domain Status: clientTransferProhibited
Registrant ID: TOD-43737096
Registrant Name: Whois Agent
Registrant Organization: Whois Privacy Protection Service
Registrant Address1: Xiamen
Registrant City: Xiamen
Registrant State/Province: FUJIAN
Registrant Postal Code: 361000
Registrant Country: China
Registrant Country Code: CN
Registrant Phone Number: +57.59222577844
Registrant Facsimile Number: +57.59222577844
Registrant Email: firstname.lastname@example.org
Name Server: NS1.ZAEHROMFUY.IN
Name Server: NS2.ZAEHROMFUY.IN
Created by Registrar: TODAYNIC.COM, INC.
Last Updated by Registrar: TODAYNIC.COM, INC.
Domain Registration Date: Thu Jul 10 09:26:06 GMT 2014
Domain Expiration Date: Thu Jul 09 23:59:59 GMT 2015
Domain Last Updated Date: Thu Jul 10 09:26:07 GMT 2014
In the original GameOver Zeus, the domain generation algorithm and its associated command and control resources serves the botnet as a fallback to the peer-to-peer botnet which serves as this malware’s primary means of distributing instructions to infected machines. Using the websites associated with the domain generation algorithm the GameOver botnet operators may distribute commands to infected machines with which the peer-to-peer botnet has lost contact.
The binary that is dropped and injected into Internet Explorer after contacting the C&C is randomly named. The version seen this afternoon is currently detected by 8 of 54 AV products at VirusTotal, though others may detect it using non-signature based methods.
A little over a month ago the GameOver Zeus botnet suffered a major blow as law enforcement carried out a takeover of the domains associated with the domain generation algorithm and made efforts to remove this malware from infected machines. Both actions severely limited the ability for botnet operators to issue commands to victims’ machines.
These efforts seemed to halt the spread of this dangerous malware and led to its disappearance from malicious spam emails.
Malcovery was able to identify a number of the command-and-control hosts believed to be involved in this attempt to revive the GameOver botnet. Following contact with any of these hosts, the malware began to exhibit behaviors characteristic of the GameOver trojan—including the characteristic list of URLs and URL substrings targeted by the malware for Web injects, form-grabs, and other information stealing capabilities.
This discovery indicates that the criminals responsible for GameOver’s distribution do not intend to give up on this botnet even after suffering one of the most expansive botnet takeovers/takedowns in history.
As always, Malcovery’s analysts are watching this situation closely and will provide the most meaningful threat intelligence regarding further developments regarding the GameOver Zeus trojan.