Domain Fronting, Phishing Attacks, and What CISOs Need to Know

CISO Summary

Cofense IntelligenceTM is seeing continued use of a cyber-attack technique known as domain fronting. It’s yet another way hackers conceal their malicious activity, in this case using work-arounds to evade security controls and gain access to command-and-control (C2) infrastructure (scroll down for a technical explanation).

Cozy Bear, the Russian threat actors, used similar tactics when they hacked the Democratic National Committee in 2016. Today, businesses are dealing with phishing and malware attacks that domain fronting enables.

While Google and Amazon have taken measures in their CDNs to curtail this trend, we have seen an uptick in C2 infrastructure hosted in Cloudflare CDNs (figures 2-4 below). Last month, Cofense Intelligence reported that Cloudflare domains were being abused by threat actors to launch malware attacks on finance departments.

Why is this a problem?

If part of your cyber defense strategy is using a web gateway to prevent employees from visiting non-categorized sites, or blocking based on a threat intelligence feed of known C2 hosts, you can’t practically block access to a CDN without disrupting Internet-reliant business processes.

CISOs should make sure their SOCs are aware of the problem when reviewing suspicious emails reported by employees. While we wait for traditional cyber perimeter controls to catch up to this threat, a phishing training and reporting program (see Cofense PhishMeTM and Cofense ReporterTM), plus a phishing-specific response capability (see Cofense TriageTM and Cofense VisionTM) is the last line of defense.

Full Details

Malware operators continue to use domain fronting to bypass security measures and reach their command and control (C2) infrastructure hosted on content delivery networks (CDN). This C2 communication technique is difficult to defend against due to the large overhead required and strong reliance on CDNs. Certain CDN providers have recently changed their network schemes and policies in response to this threat, however, domain fronting is still possible through some of the minor CDN hosts.

Domain fronting is the exploitation of an encrypted connection to a CDN to gather web resources otherwise blocked by network security measures.

  • First, the client initiates a connection to a legitimate domain (front domain) via HTTP.
  • Second, the originating connection request is read in the clear and is inspected by network security measures.
  • Third, an HTTPS connection is created when the connection is encrypted with an SSL layer, allowing the contents of the traffic to bypass inspection.
  • Finally, The HTTP Host header is read by the server for the resources needed.

The HTTP host header, for this technique, is manipulated to gather resources from a nefarious site on the same CDN. The connection to the manipulated HTTP host header inside the encrypted traffic bypasses network security measures that don’t decrypt the traffic.

For domain fronting to work, the nefarious site and the legitimate site must both be hosted by the same CDN. The ability to pull resources from other sites works because of the inner networking of the CDN and the routing access availability to other parts of their hosting environment. This technique is also utilized with The Onion Router (TOR) node bridges and the meek protocol. The Russian hacker group that breached the Democratic National Committee in 2016, APT29, also known as Cozy Bear, used the TOR meek protocol for their C2 infrastructure communication. Figure 1 gives an overview of this technique.

Figure 1 Technique of domain fronting to bypass inspection.

Google and Amazon CDNs mitigated this technique by preventing any routing from one owner’s site to another. This is done by matching the HTTP host header with the original server name indication (SNI) request, implemented in late April and early May 2018. Since then, Cofense Intelligence has seen an increase in the number of phishing campaigns delivering malware in which the C2 was hosted by Cloudflare.

Figure 2 shows the contrast in Cloudflare C2 seen used by malware before and after May 2018, when Google and Amazon imposed barriers to such activity on their CDNs.

Figure 2 Analyzed C2’s hosted on Cloudflare before and after May 2018.

Figure 3 shows the breakdown of malware families that have used Cloudflare for C2 infrastructure after May of this year.

Figure 3 Malware families utilizing C2’s hosted by Cloudflare since May 2018.

Figure 4 shows the number of different hosts hosted by Cloudflare to which each malware family connects.

Figure 4 Number of C2’s hosted by Cloudflare for each malware family.

Domain fronting has been used by hacktivists and threat actors like APT29 to conceal their malicious activity. CDNs are starting to take the necessary steps to mitigate domain fronting by negating routing from one owner’s site to another, but this ability still persists because it allows for routing to take place among a single owner’s sites.

Defending against this type of communication is a heavy lift for the information technology team. Stopping a malicious email campaign within the email security stack before it gets to the end user’s inbox, and training users to identify phish that do reach their inboxes, are keys to helping mitigate this evasive exfiltration techniques like domain fronting.

Learn more about how Cofense stops active phishing threats.

 

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TV-License Phishing Scam Tricks UK Users Into Giving Personal Information

Cofense Intelligence recently observed a new phishing scam making the rounds in the United Kingdom. It poses as the TV licensing authority better known as the British Broadcasting Corporation. The premise behind the scam is to trick the user into believing that he or she is breaking the law by not owning a valid license to receive TV, a criminal offense in the UK with a maximum penalty of a £1000 fine plus any legal costs incurred during prosecution.  

2018: A Reverse-Course for Ransomware

By Mollie MacDougall

The overall number of ransomware campaigns and active families has declined precipitously in 2018 as compared to last year, almost certainly due to multiple deterrents and a better alternative for profit-minded hackers. This reverse-course in ransomware trends follows years of sustained growth in the number of ransomware families and unique campaigns. Still, ransomware attacks make headlines and will likely continue into next year.

Bah HumBUG: 5 Recent Holiday Phishing Samples You Need to Watch Out For

Along with more online shopping, correspondence, and travel, the holiday season sees an increase in phishing operators eager to capitalize on a more-active attack surface. With Thanksgiving tomorrow, Cofense Intelligence and the Cofense Phishing Defense Center have seen a bombardment of Thanksgiving-themed phishing lures this week. Threat actors use this inundation of emails to their advantage—hoping to trick anyone looking for a good deal or eager to partake in the season’s merriment.

Major US Financial Institutions Imitated in Advanced Geodo/Emotet Phishing Lures that Appear More Authentic by Containing ProofPoint URL Wrapped Links

By Darrel Rendell, Mollie MacDougall, and Max Gannon

Cofense IntelligenceTM has observed Geodo (also known as Emotet) malware campaigns that are effectively spoofing major US financial institutions in part by including legitimate URLs wrapped in Proofpoint’s (PFPT) TAP URL Defense wrapping service. This adds an air of legitimacy to the casual observer, designed to increase the chances of malware infection.

Figures 1 and 2 provide examples of the template and URL wrapping. Cofense Intelligence assesses the improved phishing templates are likely based upon data pilfered with a recently updated scraper module to spoof US financial institutions so effectively.

Figure 1: email template spoofing a major US financial institution

Figure 2: Proofpoint’s URL Wrapping service appearing within this campaign

After a month-long hiatus, Geodo returned on November 6th, 2018 with upgrades to its spamming module, supplementing existing capabilities – namely contact list and signature block theft – with functionality enabling the theft of up to 16KB of raw emails and threads. Although the exact reason for this module upgrade was unclear, Cofense Intelligence assessed it would either be used to bolster the actors’ social engineering efforts, using the stolen data to refine Geodo phishing templates, or for direct revenue generation – selling the raw message content to the highest bidder.  Today, it appears the initial prediction was correct.

The campaign observed on November 13th was, in many ways, a standard Geodo campaign: messages distributed en masse to targets across the globe, spoofing a known and trusted organization, containing URLs (Table 1) pointing to Word documents containing hostile macros (Table 2). When executed, these macros retrieve a fresh sample of Geodo from one of five compromised web servers and execute it on the machine. As has become increasingly common with Geodo campaigns, the malware functioned as a downloader for other payloads, in this case retrieving a sample of IcedID.

IcedID shares some basic behavior with TrickBot—another prolific banking trojan turned multipurpose botnet. However, IcedID targets both investment and financial institutions as well as several bank holding companies many of which even TrickBot does not target, as TrickBot is much less focused on investment banks or smaller US commercial banks. An example of an IcedID spoofed login page for a regional US bank can be seen in Figure 3.

Figure 3: a spoofed login page for a regional bank that led to a Geodo and subsequent IcedID payload

Geodo has always been a formidable botnet and continues to grow. During tracking, we have seen at least 20,000 credentials added to the list of credentials used by the botnet clients each week along with millions upon millions of recipients. The introduction of this new module has had clear and dramatic effects on the sophistication and efficacy of this social engineering effort. In July, Geodo began including more sophisticated phishing lures, imitating US banks and including graphics that made the emails look less generic and more convincing.

This most recent campaign demonstrated a shocking improvement from that initial upgrade, demonstrating the value of the email scraping module. Considering that where Geodo goes, TrickBot often follows, we are concerned that this type of module will show up in other malware campaigns. The new inclusion of ProofPoint URLs wrapped with URL Defense adds an additional false sense of security to a user and may indicate the malware scraped the wrapped URLs from a compromised user.

Several members of the Cofense Intelligence team discussed Geodo in a recent open customer call. Any customers who were unable to attend are welcome to email mark.adams@cofense.com for a recording.

Cofense is also offering a complimentary Domain Impact Assessment, powered by the Cofense Research and Intelligence teams, for any organization that may be affected by this Geodo update. Learn more here.

Table 1: Payload URLs observed during this campaign

Table 2: Files associated with this campaign

Table 3: Command and Control infrastructure identified during this campaign

All third-party trademarks referenced by Cofense whether in logo form, name form or product form, or otherwise, remain the property of their respective holders, and use of these trademarks in no way indicates any relationship between Cofense and the holders of the trademarks.