The Weaponized Shortcut

LNK files — Windows shortcut files — are designed to make our lives easier. They point users toward applications, documents and directories, allowing them to access content quickly without spelunking through dozens of folder paths. They’re small, flexible, and generally considered to look innocuous.

And that’s exactly what makes them dangerous.

Threat actors can manipulate LNK files to far exceed their file- and folder-opening mandate. In the hands of a sophisticated attacker, LNK files become stealthy execution vehicles capable of executing and launching malware without raising any alarm bells. These tiny shortcut attachments can be the first step in a cascade of attacks.

Understanding LNK Files

Understanding how LNK files are intended to operate is a key part of grasping the risk they pose in file upload environment.

LNK files are designed to be quick access points to executable files or applications in a system. This ensures programs don’t have to be duplicated throughout a system for users to access them outside their home folder. LNK files point to the original file’s location on disk, and they store metadata including the target path, working directory, and – in some cases – custom icons or arguments used during execution.

It’s no exaggeration to say LNKs are a staple of the Windows user interface; they fundamentally improve user experience on the OS. They’re used widely across desktops, Start menus, and file explorers to make accessing programs and files as easy as possible. Because LNKs are so commonplace (and often overlooked), they present a unique challenge from a security perspective. They can appear benign – seemingly pointing to a harmless application or document – all while carrying malicious payload injections.

Why Attackers Leverage LNK Files

The fact that LNKs are inherently executable makes them an obvious target for attackers. They don’t require macros or complex user interactions to trigger; they can execute payloads the moment a user clicks on them. In many cases, the victim won’t even notice anything unusual is happening in the background.

Malicious LNKs are often disguised with icons familiar to Windows users – like PDF, folder icons, Word docs, Excel docs, etc. – and they tend to bear misleading, trustworthy names. Default Windows behavior will inherently hide double extensions like “file.pdf.lnk”, which further reduces user suspicion (users will only see “file.pdf” before they click on the file in question). Some phishing campaigns have also involved compressing LNKs inside ZIP or RAR archives to bypass email filters.

It’s common for threat actors to craft LNK files which appear to open a specific document or folder in the user’s environment – but actually run PowerShell or CMD commands to download and execute remote malware in the background. It’s not just a theoretical risk; it’s one of the most actively exploited file types in modern cyberattacks.

Real-World Attacks with LNK: APT28 in Focus

In 2017, APT28 (also known as Fancy Bear or Sofacy) launched a targeted cyber campaign against certain entities in Japan. A key element of the attack involved the use of malicious LNK files embedded within ZIP archives.

One executed by unsuspecting users, these shortcut files triggered PowerShell scripts that downloaded and executed secondary payloads. This effectively compromised victims’ machines without raising immediate suspicion – a key factor in the success of any large-scale cyberattack.

While this case occurred 8 years ago, it nevertheless reinforces why LNK files are such a dangerous format: they provide attackers with the ability to execute arbitrary commands while appearing as ordinary files to the end user.

Case in Point: CVE-2020-16933

An incident from 2020 serves as another interesting example of LNK exploitation. CVE-2020-16933 exposed a security bypass in Microsoft Word which allowed attackers to use malicious LNK files to execute commands as the current user. In this case, no advanced privilege escalation or exotic techniques were required; a threat actor simply needed to convince a victim to open a Word document containing a specially crafted LNK reference.

While this flaw has since been patched, it still highlights a broader issue: even the most trusted applications can mishandle shortcut files in dangerous ways.

This vulnerability also served as a reminder that file security isn’t just about blocking certain file types we know might be dangerous — it’s also about understanding how those files behave after they’re processed.

Why File Filtering Often Fails

The unfortunate reality is that file filtering approaches — such as checking extensions, verifying MIME types, or running lightweight antivirus (AV) scans to check for malware signatures — are often ineffective against LNK attacks.

It’s critically important to remember that a malicious LNK file doesn’t need to hide a virus directly, it just needs to point to one. Unless an AV scanner inspects the commands embedded within an LNK shortcut and understands exactly what they’re pointing to, it won’t detect the underlying threat.

Some weakly configured security tools even skip LNKs altogether, treating them as low-risk or system-native files. This assumption can be catastrophic, and it’s a threat actor’s dream come true.

Deconstructing LNK Files with the Cloudmersive Virus Scan API

The Cloudmersive Advanced Virus Scan API inspects the command execution path embedded in LNK shortcuts, analyzes shell commands for signs of obfuscation or remote access behavior, and checks whether embedded links point to dangerous payloads.

The API’s behavioral detection engine inspects what the LNK is attempting to do, not just what it claims to be. It flags suspicious command-line operations, checks for encoded PowerShell strings, and traces the execution chain down to the payload.

Along with deep content verification, it also leverages a continuously updated list of 17 million+ virus and malware signatures to identify known malware threats. The threat database is updated every 15 minutes with new data from public, private, and Cloudmersive research databases.

Proceed with Caution

LNK files need to be inspected deeply, just like any other executable. It’s important to treat every shortcut as a potential security risk until it’s proven safe. That can mean deleting LNKs outright or quarantining them for further analysis.

To learn more about blocking LNK threats with the Cloudmersive Advanced Virus Scan API, please feel free to contact a member of our team.