Pierluigi Paganini January 29, 2015

The Dell SecureWorks Counter Threat Unit (CTU) research team observed the ZeroAccess botnet resumes again with click-fraud activity.

Law enforcement has destroyed the ZeroAccess botnet, also known as Sirefef, in December 2013 by a joint effort of Microsoft Digital Crimes Unit, FBI, Europol and industry partners.

The ZeroAccess botnet is considered one of most insidious malicious architecture that has infected nearly two million systems all over the world, the majority of computers ZeroAccess has infected have been located in the U.S. and Western Europe.  Richard Domingues Boscovich, assistant general counsel with Microsoft Digital Crimes Unit, estimated that ZeroAccess cost online advertisers upwards of $2.7 million each month.

Trojan. ZeroAccess malware uses an advanced rootkit to hide itself and it is able to download more malware and opens a backdoor on the victim’s computer.
The name ZeroAccess derives from a string found in the kernel driver code that is pointing to the original project folder called ZeroAccess, it is distributed through several means including compromised websites, redirecting traffic to malicious websites that host the trojan and distribute it using exploit kit such as the BlackholeExploit Toolkit. The ZeroAccess bot exploits a “drive-by download” scheme for infection process and is able to update itself through peer-to-peer networks. The monetization process behind the ZeroAccess botnet is a classic pay per click advertising, the malware download an application that conducts Web searches and clicks on the results.

“This is known as click fraud, which is a highly lucrative business for malware creators.” states the Symantec advisor on the agent.

Almost every search engine and browser was targeted by ZeroAccess including Google, Bing and Yahoo.

Between March 21, 2014, and July 2, 2014, the researchers at SecureWorks Counter Threat Unit (CTU) collected evidence of ZeroAccess botnet activity. On Jan. 15 2015, the new ZeroAccess botnet was distributing click fraud templates to compromised machines.

The experts explained that the current ZeroAccess botnet is composed of residual machines from past compromises and is smaller than original botnet. At the moment ZeroAccess appears segmented into two distinct botnets that operate separately with Windows systems running on a 32-bit architecture and on a 64-bit architecture.

“The threat actors behind ZeroAccess have not attempted to expand the botnet with new compromises following the December 2013 disruption,” reprtes a blog post published by CTU. “Instead, the botnet is composed of residual hosts from past compromises, so it is much smaller than it has been in the past. ZeroAccess is segmented into two distinct botnets that operate over different UDP ports: UDP 16464/16471 — used by compromised Windows systems running on a 32-bit architecture (and) UDP 16465/16470 — used by compromised Windows systems running on a 64-bit architecture.”

Each machine acts as nodes in the P2P network, and periodically receives new templates that include URLs for attacker-controlled template servers.

“Compromised systems act as nodes in the P2P network, and they periodically receive new templates that include URLs for attacker-controlled template servers,” the researchers noted. “After the systems visit these URLs, the malware begins a cascade of redirects that eventually lead to a Traffic Direction System (TDS) that sends the bot to its final destination.”

Experts at SecureWorks have spotted 55,208 unique IP addresses composing the ZeroAccess botnet between January 17 and January 25, 2015. During this period, the peer-to-peer network had 38,094 hosts in the 16464/16471 (32-bit) segment and 17,114 hosts in the 16465/16470 (64-bit) segment participating.

Below the lists of countries with the highest number of infections.

“Although the threat actors behind ZeroAccess have not made any measurable attempts to augment the botnet in more than a year, it remains substantial in size,” according to the researchers. “Its resiliency is a testament to the tenacity of its operators and highlights the danger of malware using P2P networks. ZeroAccess does not pose the same threat as other botnets used to perpetrate banking fraud, steal login credentials and valuable data, or hold victims’ files for ransom. However, it does cause untold fraud losses for advertisers and consumes considerable resources for organizations with compromised hosts.”

Pierluigi Paganini

(Security Affairs – ZeroAccess, botnet)