Malicious NPM packages are part of a malware “barrage” hitting repositories

Researchers have found another 17 malicious packages in an open source repository, as the use of such repositories to spread malware continues to flourish.

This time, the malicious code was found in NPM, where 11 million developers trade more than 1 million packages among each other. Many of the 17 malicious packages appear to have been spread by different threat actors who used varying techniques and amounts of effort to trick developers into downloading malicious wares instead of the benign ones intended.

This latest discovery continues a trend first spotted a few years ago, in which miscreants sneak information stealers, keyloggers, or other types of malware into packages available in NPM, RubyGems, PyPi, or another repository. In many cases, the malicious package has a name that’s a single letter different than a legitimate package. Often, the malicious package includes the same code and functionality as the package being impersonated and adds concealed code that carries out additional nefarious actions.

A ripe attack vector

“We are witnessing a recent barrage of malicious software hosted and delivered through open-source software repositories,” JFrog researchers Andrey Polkovnychenko and Shachar Menashe wrote on Wednesday. “Public repositories have become a handy instrument for malware distribution: the repository’s server is a trusted resource, and communication with it does not raise the suspicion of any antivirus or firewall. In addition, the ease of installation via automation tools such as the npm client, provides a ripe attack vector.”

Most of the packages JFrog flagged stole credentials or other information for Discord servers. Discord has become a popular platform for people to communicate through text, voice, and video. Compromised servers can be used as command and control channels for botnets or as a proxy when downloading data from a hacked server. Some packages stole credit card data associated with hacked Discord accounts.

Two packages—discord-lofy and discord-selfbot-v14—came from an author using the name davisousa. They masquerade as modifications of the popular legitimate library discord.js, which enables interaction with the Discord API. The malware incorporates the original discord.js library as its base and then injects obfuscated malicious code into one of the package files.

The JFrog researchers wrote:

The obfuscated version of the code is enormous: more than 4,000 lines of unreadable code, containing every possible method of obfuscation: mangled variable names, encrypted strings, code flattening and reflected function calls:

Through manual analysis and scripting, we were able to deobfuscate the package and reveal that its final payload is quite straightforward—the payload simply iterates over the local storage folders of well-known browsers (and Discord-specific folders), then searches them for strings looking like a Discord token by using a regular expression. Any found token is sent back via HTTP POST to the hardcoded server https://aba45cf.glitch.me/polarlindo.

Another package named fix-error claimed to to fix errors in a discord “selfbot.” It, too, contained malicious code that had been obfuscated but, in this case, was much easier for the researchers to deobfuscate. The researchers soon determined that the hidden code was a stolen version of the PirateStealer, an app that steals credit card information, login credentials, and other private data stored in a Discord client. It works by injecting malicious Javascript code into the Discord client. The code then “spies” on the user and sends the stolen information to a hardcoded address.

A third example is prerequests-xcode, a package that contains remote access trojan functionality. The researchers wrote:

When inspecting the package’s code, we identified it contains a Node.JS port of
DiscordRAT(originally written in Python) which gives an attacker full control over the victim’s machine. The malware is obfuscated with the popular online tool obfuscator.io, but in this case it is enough to inspect the list of available commands to understand the RAT’s functionality (copied verbatim).

The full list of packages is:

As noted earlier, NPM isn’t the only open source repository to be infiltrated with malicious packages. The PyPi repository for Python has seen its share of malware-laden packages, as has RubyGems.

People downloading open source packages should take extra care in making sure the item they’re downloading is legitimate and not malware masquerading as something legitimate. Larger organizations that rely heavily on open source software may find it useful to purchase package management services, which JFrog just happens to sell.