On the 21st of July, 2014, Cisco TRAC became aware that the website dwnews.com was serving malicious Adobe Flash content. This site is a Chinese language news website covering events in East Asia from a US base. The site is extremely popular, rated by Alexa’s global traffic ranking as the 1759th most visited website worldwide, and the 28th most visited in South Korea. In addition the news site also receives a substantial number of visitors from Japan, the United States and China.
This malware campaign does not appear to be tightly targeted. Twenty-seven companies across eight verticals have been affected:
Banking & Finance Energy, Oil, and Gas Engineering & Construction Insurance Legal Manufacturing Pharmaceutical & Chemical Retail & Wholesale
This is indicative of the campaign acting as a drive-by attack targeting anyone attempting to view one of the affected sites.
In part one of our two part blog series on the “String of Paerls” threat, we showed an attack involving a spearphish message containing an attached malicious Word doc. We also described our methodology in grouping similar samples based on Indicators of Compromise: static and dynamic analysis indicators. In this second part of the blog series we will cover the malicious documents and malicious executables. For the technical deep dive see the write up on the VRT blog here.
This is part one in a two-part series due to the sheer amount of data we found on this threat and threat actor. This particular attack was a combined spearphishing and exploit attempt. As we’ve seen in the past, this can be a very effective combination.
In this specific example the attackers targeted a feature within Microsoft Word — Visual Basic Scripting for Applications. While basic, the Office Macro attack vector is obviously still working quite effectively. When the victim opens the Word document, an On-Open macro fires, which results in downloading an executable and launching it on the victim’s machine. This threat actor has particularly lavish tastes. This threat actor seem to target high-profile, money-rich industries such as banking, oil, television, and jewelry.
Discovering the threat
The VRT has hundreds of feeds of raw threat intelligence, ranging from suspicious URLs, files, hashes, etc. We take that intelligence data and apply selection logic to it to identify samples that are worthy of review. Using various methods from machine learning to dynamic sandbox analysis, we gather details about the samples -- producing indicator of compromise (IOC), and alerts made up of multiple IOCs.
During our analysis we took the last 45 days’ worth of samples, and clustered them together based on a matching set of alert criteria. This process reduced over a million detailed sample reports to just over 15 thousand sample clusters that exhibit similar behavior. Using this pattern of similar behavior, we were capable of identifying families of malware. This led us to discover a Microsoft Word document that downloaded and executed a secondary sample, which began beaconing to a command and control server.
The Malicious Word documents & Associated Phishing campaign
The attacks we uncovered are an extremely targeted spear phish in the form of an invoice, purchase order, or receipt, written specifically for the recipient. For instance, the following is an example message we observed that purportedly came from “Maesrk”, the shipping company.
This post is co-authored by Andrew Tsonchev, Jaeson Schultz, Alex Chiu, Seth Hanford, Craig Williams, Steven Poulson, and Joel Esler. Special thanks to co-author Brandon Stultz for the exploit reverse engineering.
Silverlight exploits are the drive-by flavor of the month. Exploit Kit (EK) owners are adding Silverlight to their update releases, and since April 23rd we have observed substantial traffic (often from Malvertising) being driven to Angler instances partially using Silverlight exploits. In fact in this particular Angler campaign, the attack is more specifically targeted at Flash and Silverlight vulnerabilities and though Java is available and an included reference in the original attack landing pages, it’s never triggered.
HTTP requests for a specific Angler Exploit Kit campaign
Angler exploit content types delivered to victims, application/x-gzip (Java) is notably absent
As of May 1, 2014, we can confirm Cisco customers have been targets of this attack. For the latest coverage information and additional details see our new post on the VRT blog.
Protecting company critical assets is a continuing challenge under normal threat conditions. The disclosure of zero-day exploits only makes the job of IT security engineers that much harder. When a new zero-day vulnerability was announced on April 26, 2014 for Microsoft Internet Explorer, corporate security organizations sprang into action assessing the potential risk and exposure, drafting remediation plans, and launching change packages to protect corporate assets.
Some companies however, rely on Managed Security Services to protect those same IT assets. As a Cisco Managed Security services customer, the action was taken to deploy updated IPS signatures to detect and protect the companies critical IT assets. In more detail, the IPS Signature team, as a member of the Microsoft Active Protections Program (MAPP), developed and released Cisco IPS signature 4256/0 in update S791 and Snort rules 30794 & 30803 were available in the ruleset dated 4-28-2014. The Cisco Managed Security team, including Managed Threat Defense, received the update as soon as it became available April 28th. Generally, Cisco Managed Security customers have new IPS signature packs applied during regularly scheduled maintenance windows. In the event of a zero-day, the managed security team reached out to customers proactively to advise them of the exploit and immediately were able to apply signature pack updates to detect and protect customer networks.
While corporate security organizations must still assess ongoing risks and direct overall remediations to protect corporate data, Cisco can take the actions to provide security visibility into the targeted attacks, increase protection with fresh signatures, and reduce risk profile for the corporate InfoSec program.
For more detail on the vulnerability, please see Martin Lee’s blog post.
More details about this exploit and mitigation information can be found on the following links: