This post was authored by Nick Biasini
On January 27th, Talos researchers began observing a new Angler Exploit Kit (EK) campaign using new variants associated with (CVE-2015-0311). Based on our telemetry data the campaign lasted from January 26th until January 30th with the majority of the events occurring on January 28th & 29th.
Researchers detected the new campaign when referencing a known hash that was delivering the recent Flash 0-day (CVE-2015-0311). During this investigation several layers of subdomains are being used to avoid detection. As of the writing of this blog ~1800 domains have been seen being used by the following IP addresses:
These domains are associated with the landing page and exploits. None of the actual root domains appear to be compromised and are legitimately registered to owners. It appears that the actors have managed to compromise a large group of registrant accounts and have set up subdomains (i.e. acfbbfhdahfeh.legitdomain.info). There are enough of these domains that some of them are only seen once before being abandoned. The majority of the compromised domains are registered through GoDaddy and it appears that 50+ accounts have been compromised. Many of these accounts control multiple domains with some controlling 45+ unique domains. Below is a sample showing a small portion of the subdomains that were registered to a single domain all resolving to a single IP address.
To take the approach a step further these actors have utilized another tier of the subdomains to serve as the initial redirection page. Our telemetry data points to another ~650 of these subdomains linked back to a single IP address, 188.8.131.52. The main distribution method is malvertising with the malicious advertisement pointing to an initial tier of compromised subdomains. These sites then redirect to another subdomain delivering landing page and exploitation. These actors have been seen serving both Adobe Flash and Silverlight exploits, which will be discussed in more detail below.
The exploits that are being served are a combination of known and new variants of existing vulnerabilities. The first and most commonly served sample:
is the widely distributed version of the Flash 0-day for Angler Exploit Kit (details). The second groups of samples were Silverlight based, which are known to be part of the Angler EK, as Talos has discussed previously.
There is an additional group of hashes that are all variants of CVE-2015-0311 but have very low detection rates currently (Between 1/57 – 3/57)
Despite the low Anti-Virus detection rates, Cisco AMP and Network Security IDS & NGFW successfully detected and blocked the new variants as well as the older samples.
This is another example of how Angler Exploit Kit continues to differentiate itself. It changes and evolves on a constant basis producing new variation on the existing exploits as well as providing enough customization on the recent vulnerability (CVE-2015-0311) to effectively avoid reliable detection. If the first month of 2015 is any indication, the Angler Exploit Kit could have a big year.
Snort Rules: 33271-33274, 33286 for the most up to date list please refer to Defense Center
Protecting Users Against These Threats
Advanced Malware Protection (AMP) is ideally suited to prevent the execution of the malware used by these threat actors.