Security research firm ESET found that content delivery networks (CDNs) offer more than just ways to optimize bandwidth: They can also be a source of malware.

ESET observed certain methods that are being put into use as the basis for a new kind of attack, including the use of remote scripts and command-and-control (C&C) techniques, reported We Live Security.

The first step in the attack is to store a small bit of JavaScript code in a file located at a particular address on the CDN, according to SecurityWeek.

This bit of JavaScript is used by a Nullsoft Scriptable Installer System (NSIS) program to perform the first part of the malware installation. The threat actors have to get the victim to activate the NSIS, and that is where the social engineering part comes into action. They make the victim believe that this NSIS downloader is something else they want, and the victim does whatever action is needed to execute the NSIS.

The downloader will then go to the JavaScript snippet and obtain it. Next, the eval function is called to evaluate the snippet and create additional parts to the snippet. The form of the addition is: downAndExec(\”<parameter_1>\”, \”<parameter_2>\”). ESET said that the first parameter (<parameter_1>) will correspond to the URL where the C&C is hosted, and the second parameter (<parameter_2>) contains the “x-id” data that is necessary to download other payloads.

This framework has enough functionality to get various modules from the C&C and execute them individually. One example of this technique used Facebook’s content delivery network to load a banking Trojan that worked only for Brazilian banks.

SecurityWeek noted that protection against sandboxing has been implemented in the bank Trojan downloader. That means the malicious code will not be executed if the JavaScript snippet is analyzed separately, which would indicate a sandbox function. The script also directly identifies whether the machine meets its needs by performing other checks before it takes any malicious action.

Content delivery networks present a number of problems for malware detection along with their intended use. For example, the IP of such a network is virtually unblockable if it is delivering malware. Blocking the IP will not work in this case due to a flood of uncompromised information originating from the malware. Additionally, finding appropriate IoCs may be hard due to the high volume of traffic originating from such a site.

Like fileless malware, this kind of security challenge requires different methods to both detect it and to mitigate it. However, the advice of not clicking on unknown links or documents remains as apt as ever.

More from

More School Closings Coast-to-Coast Due to Ransomware

Instead of snow days, students now get cyber days off. Cyberattacks are affecting school districts of all sizes from coast-to-coast. Some schools even completely shut down due to the attacks. The federal government recently warned that K-12 schools face a growing threat from cyber groups. According to the FBI, school districts often have limited cybersecurity protections, which makes them even more vulnerable. The FBI also says it anticipates the number of threats to increase. In a recent warning, the nation’s…

The Role of Human Resources in Cybersecurity

The human resources (HR) department is an integral part of an organization. They work with all departments with a wider reach than even IT. As a highly visible department, HR can support and improve an organization’s security posture through employee training. Their access to employees at the start of employment is an opportunity to lay a foundation for a culture of risk awareness. HR departments do not typically include cybersecurity risk awareness training with new hire onboarding, but it’s something…

New Attack Targets Online Customer Service Channels

An unknown attacker group is targeting customer service agents at gambling and gaming companies with a new malware effort. Known as IceBreaker, the code is capable of stealing passwords and cookies, exfiltrating files, taking screenshots and running custom VBS scripts. While these are fairly standard functions, what sets IceBreaker apart is its infection vector. Malicious actors are leveraging the helpful nature of customer service agents to deliver their payload and drive the infection process. Here’s a look at how IceBreaker…

Operational Technology: The evolving threats that might shift regulatory policy

Listen to this podcast on Apple Podcasts, Spotify or wherever you find your favorite audio content. Attacks on Operational Technology (OT) and Industrial Control Systems (ICS) grabbed the headlines more often in 2022 — a direct result of Russia’s invasion of Ukraine sparking a growing willingness on behalf of criminals to target the ICS of critical infrastructure. Conversations about what could happen if these kinds of systems were compromised were once relegated to “what ifs” and disaster movie scripts. But those days are…