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Threat Spotlight: Cisco Talos Thwarts Access to Massive International Exploit Kit Generating $60M Annually From Ransomware Alone

This post was authored by Nick Biasini with contributions from Joel Esler, Nick Hebert, Warren Mercer, Matt Olney, Melissa Taylor, and Craig Williams.

Executive Summary

Today, Cisco struck a blow to a group of hackers, disrupting a significant international revenue stream generated by the notorious Angler Exploit Kit.  Angler is one of the largest exploit kit found on the market and has been making news as it has been linked to several high-profile malvertising/ransomware campaigns. This is the most advanced and concerning exploit kit on the market – designed to bypass security devices and ultimately attack the largest number of devices possible.

In its research, Cisco determined that an inordinate number of proxy servers used by Angler were located on servers of service provider Limestone Networks ­ — with the primary threat actor responsible for up to 50 percent of Angler Exploit Kit activity, targeting up to 90,000 victims a day, and generating more than $30M annually.  This implies that if you apply the full scope of Angler activity the revenue generated could exceed $60M annually. Talos gained additional visibility into the global activity of the network through their ongoing collaboration with Level 3 Threat Research Labs. Finally, thanks to our continued collaboration with OpenDNS we were able to gain in-depth visibility into the domain activity associated with the adversaries.

Cisco then took action:

  • Shutting down access for customers by updating products to stop redirects to the Angler proxy servers.
  • Released Snort rules to detect and block checks from the health checks
  • All rules are being released to the community through  Snort
  • Publishing communications mechanisms including protocols so others can protect themselves and customers.
  • Cisco is also publishing IoCs so that defenders can analyze their own network activity and block access to remaining servers

This is a significant blow to the emerging hacker economy where ransomware and the black market sale of stolen IP, credit card info and personally identifiable information (PII) are generating hundreds of millions of dollars annually.

Watch Angler compromise a box and install ransomware at the end of the video.

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Vulnerability Spotlight: MiniUPnP Internet Gateway Device Protocol XML Parser Buffer Overflow

Vulnerability discovered by Aleksandar Nikolic of Cisco Talos. Post authored by Earl Carter and William Largent

Talos is disclosing the discovery of an exploitable buffer overflow vulnerability in the the MiniUPnP library TALOS-2015-0035 (CVE-2015-6031). The buffer overflow is present in client-side XML parser functionality in miniupnpc. A specially crafted XML response can lead to a buffer overflow, on the stack, resulting in remote code execution.

This miniupnpc buffer overflow is present in client-side part of the library. The vulnerable code is triggered by an oversized XML element name when applications using miniupnpc library are doing initial network discovery upon startup, while parsing the replies from UPNP servers on the local network.

MiniUPnP is commonly used to allow two devices which are behind NAT firewalls to communicate with each other by opening connections in each of the firewalls, commonly known as “hole punching”. Various software implementations of this technique enable various peer-to-peer software applications, such as Tor and cryptocurrency miners and wallets, to operate on the network.

When parsing the UPNP replies, the XML parser is initialized and `parsexml()` function is called:


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Down the Rabbit Hole: Botnet Analysis for Non-Reverse Engineers

This post is authored by Earl Carter & Holger Unterbrink.


Talos is often tasked with mapping the backend network for a specific piece of malware. One approach is to first reverse engineer the sample and determine exactly how it operates. But what if there is no time or resources to take the sample apart? This post is going to show how to examine a botnet from the Fareit family, starting with just an IP address. Then, using sandbox communities like Cisco ThreatGRID and open source products like Gephi and VirusTotal, we will track down and visualize the botnet.

Talos recently discovered some activity from the Fareit trojan. This family of malware has a significant history associated with malware distribution. It is mainly an information stealer and malware downloader network which installs other malware on infected machines. In this campaign, it mainly tries to steal Firefox and other credentials. It is possible that this botnet is sold as a pay-per-infection botnet in the underground markets. Pay-per-infection is an underground business model where criminals are paying other criminals to distribute their malware. The analysis below was mainly done in July 2015. Let’s take a walk on the wild side….

AMPs behaviour based detection found suspicious executables that downloaded files by using the following URLs in one of our customer networks.

We began analysing the infrastructure with focus on these two IP addresses and checked what other files they had been distributing. Initial analysis showed that VirusTotal found 25 and 38 files distributed from these two IP addresses. Almost all of the files in VirusTotal had different hashes, but similar or identical filenames. The following list is a sample of some of the files found in VirusTotal.

1197cb2789ef6e29abf83938b8519fd0c56c5f0195fa4cbc7459aa573d9e521b (cclub02.exe)
58f49493aa5d3624dc225ba0a031772805af708b38abd5a620edf79d0d3f7da0 (cclub02.exe)
d1b98b7b0061fbbdfc9c2a5a5f3f3bbb0ad3d03125c5a8ab676df031a9900399 (cclub02.exe)
c054e80e02c923c4314628b5f9e3cb2cad1aa9323cbcd79d34205ad1e3cad6c3 (cclub12.exe)
bd30242996a3689c36008a63d007b982d9de693766d40e43fe13f69d76e61b63 (cclub12.exe)
c609ef45f7ff918cbac24755a3a3becc65d1c06e487acd801b76a1f46e654765 (tarhun1.exe)

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SYNful Knock Scanner

This post was authored by William McVey.

Update 9/23: We updated the tool to version 1.0.1

Talos is constantly researching the ways in which threat actors are evolving to exploit systems. Recently, a piece of persistent malware coined as SYNful Knock was discovered on Cisco routers. While this malware attack is not a vulnerability, as it had to be installed by someone using valid credentials or who had physical access to the device, Cisco has published an Event Response Page for customers to provide the information needed to detect and remediate these types of attacks. We are also working with partners to identify compromised systems.

The most recent addition to the toolkit Cisco is providing customers comes after the Cisco PSIRT worked with internal teams and customers to acquire copies of the malware. Talos has now developed a tool for customers to scan their own network to identify routers that may have been compromised by this specific malware. The tool works by scanning devices and networks, looking for routers answering the SYNful Knock malware.

Note: This tool can only detect hosts responding to the malware “knock” as it is known at a particular point in time. This tool can be used to help detect and triage known compromises of infrastructure, but it cannot establish that a network does not have malware that might have evolved to use a different set of signatures.

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When Does Software Start Becoming Malware?

This post was authored by Earl Carter, Alex Chiu, Joel Esler, Geoff Serrao, and Brandon Stultz.

Defining what is malware relies on determining when undesirable behavior crosses the line from benign to clearly unwanted. The lack of a single standard regarding what is and what is not acceptable behavior has established a murky gray area and vendors have taken advantage of this to push the limits of acceptable behavior. The “Infinity Popup Toolkit” is a prime example of software that falls into this gray area by bypassing browser pop-up blocking, but otherwise exhibits no other unwanted behavior. After analyzing the toolkit, Talos determined that software exhibiting this type of unwanted behavior should be considered malware and this post will provide our reasoning.


Without a clear standard defining what is and is not acceptable behavior, identifying malware is problematic. In many situations, users are confronted with software that exhibits undesirable behavior such as the Java installer including a default option to install the toolbar. Even though many users objected to the inclusion of the toolbar, Oracle only recently discontinued including it in Java downloads after Microsoft changed their definition of malware which then classified the toolbar as malware.

There is more to unwanted software than just browser toolbars or widgets. Suppose a piece of software exhibits the following characteristics. Would this be considered malware?

  • The user was not given a choice whether or not to execute this piece of software.
  • The software was designed to specifically bypass browser security and privacy controls using clickjacking techniques.
  • The software avoids detection by encrypting portions of its payload.
  • Extensive fingerprinting (browser, plugins, operating system, and device type) takes place and sent to a third party without user consent.

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