Open-source software is everywhere. It helps power websites, mobile applications, business systems, security products and many of the digital services we use every day. It can encourage innovation, reduce costs, and allow security researchers to identify and correct problems.

We think of a cyberattack as something malicious, such as a suspicious email, a fake login page, or a virus warning. Some of the most effective attacks today use free, publicly available software known as open-source software. A recent investigation by the cybersecurity firm ReliaQuest showed exactly how this works, and what it means for anyone who uses social media on any device.

What Is Open-Source Software?

Open-source software is software whose underlying code is made publicly available for anyone to view, use, modify, and share. Open-source software is often created and maintained by communities of volunteer developers, companies, and independent contributors working together. This openness is a major reason so much of the modern internet runs on it. Web servers, programming languages, security testing tools, and even entire operating systems like Linux are open source. These tools are used because they're typically free, flexible, well-documented, and battle tested. IT professionals use open-source utilities to build websites, automate tasks, and test their own networks for weaknesses. 

The Attack: A Trusted Platform and Tool

According to ReliaQuest's threat research team, attackers recently ran a phishing campaign not through email, but through LinkedIn private messages. A user receives a message with a link to download a compressed file disguised with a legitimate-sounding name. Hidden inside that file are several components: a real, legitimate open-source PDF reader application, a malicious file disguised to look like one the PDF reader normally uses, and a portable copy of the Python programming language.

When the victim opens what they think is a PDF reader, the malicious file quietly loads instead. From there, it plants a copy of Python on the victim's computer and sets it to automatically run every time the person logs in. That hidden Python program runs an open-source script, originally built for legitimate security testing, to secretly load and execute additional malicious code. This ultimately opens the door for attackers to gain ongoing, hands-on control of the infected computer, allowing them to steal data, spy on activity, or if connected to an organization’s network, spread further to other connected computers.

Why Attackers Love Open-Source Tools

None of the software involved in this attack was custom-built malware. As ReliaQuest's researchers explain, using freely available, widely trusted tools gives criminals several advantages:

1. They blend in. Security software is often tuned to flag unfamiliar or custom-written programs. A well-known open-source tool may not raise the same alarms.

2. They save time and money. Building malware from scratch takes skill and effort. Reusing a proven, publicly available script is faster and just as effective.

3. They're hard to trace. Because open-source code is available to anyone in the world, using it "as-is" makes it much harder for investigators to link an attack back to a specific person or group.

Why Social Media Is the New Front Door

The other piece of this story is the delivery method. Email inboxes are generally protected by spam filters and phishing detection tools. Private messages on social media platforms typically are not. That gap means a person who never clicks a suspicious email link may let their guard down in a LinkedIn message, especially one that looks tailored to their job title or industry. Researchers noted that platforms popular with professionals are a goldmine for attackers looking to identify executives, IT staff, and other high-value targets simply by reading their public profiles.

What This Means for Us

You don't need to run a corporate security team to take something away from this. Some practical habits go a long way:

1. Treat social media messages with the same caution as email.  A friendly or professional-sounding message is not proof of legitimacy, especially if it includes a file to download.

2. Be wary of compressed files and executables, particularly ones sent through a chat or messaging app rather than a known, verified source.

3. Keep work and personal accounts separate. Think twice before downloading files from personal social media accounts.

4. When in doubt, verify. A quick message to the sender through a separate channel, or a call to your IT department, costs far less than a compromised system.

The bigger lesson is one that applies well beyond this specific case. Openness and trust, the very qualities that make open-source software and social media so useful, are also what make them attractive to people looking to exploit that trust. Awareness is the simplest, most effective defense available to everyone.

Karen Clay, Clay Technology and Multimedia

Courtesy, Karen Clay