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Summary
RedLine is an infostealer malware discovered in 2020. Often sold in underground forums, it is capable of stealing data such as credit card numbers, passwords, VPN and FTP credentials, gaming accounts, and even data from crypto wallets. In May 2022, Netskope Threat Labs analyzed a RedLine stealer campaign that was using YouTube videos to spread, luring victims into downloading a fake bot to automatically buy Binance NFT Mystery Boxes. Later in 2022, this malware was also spotted being self-spread through YouTube videos that were advertising popular gaming hacking tools.
In September 2022, Netskope Threat Labs found a RedLine Stealer campaign being spread through phishing emails. The email lures the user into opening a PDF file that redirects the victim to a URL that downloads RedLine, hosted on Discord.
Furthermore, we found that the attacker updated the same PDF file three times and didn’t flatten the latest version, which allowed us to retrieve three more URLs from older versions of the same file. These URLs download other malware from Discord, including PureCrypter and NjRAT (a.k.a. Bladabindi). NjRAT is another popular remote access trojan with many capabilities, such as logging keystrokes, stealing credentials from browsers, accessing the victim’s camera, managing files, and more.
In this blog post, we will analyze how this campaign works from the delivery method to the RAT payloads.
Delivery Method
The delivery method is fairly simple. The attacker sends a phishing email luring the user to open the attached PDF file, disguised as an invoice.
The PDF file contains an image that shows a blurred document, luring the user into clicking on a download icon that downloads RedLine from Discord.
By analyzing the PDF, we found older versions of the same file with different URLs the attacker was using, which are still online and delivering other malware instead of RedLine, as we will see later in this post.
This happens when the PDF is changed and isn’t flattened, keeping the update history within the objects.
RedLine Stealer
The latest URL in the PDF downloads a ZIP file from Discord that contains the RedLine Stealer payload, likely compiled on September 16, 2022.
As we covered in our previous blog, RedLine does not execute if the following countries are detected:
- Armenia
- Azerbaijan
- Belarus
- Kazakhstan
- Kyrgyzstan
- Moldova
- Russia
- Tajikistan
- Ukraine
- Uzbekistan
