閉める
閉める
明日に向けたネットワーク
明日に向けたネットワーク
サポートするアプリケーションとユーザー向けに設計された、より高速で、より安全で、回復力のあるネットワークへの道を計画します。
          Netskopeを体験しませんか?
          Get Hands-on With the Netskope Platform
          Here's your chance to experience the Netskope One single-cloud platform first-hand. Sign up for self-paced, hands-on labs, join us for monthly live product demos, take a free test drive of Netskope Private Access, or join us for a live, instructor-led workshops.
            SSEのリーダー。 現在、シングルベンダーSASEのリーダーです。
            SSEのリーダー。 現在、シングルベンダーSASEのリーダーです。
            Netskope、2024年ガートナー、シングルベンダーSASEのマジック・クアドラントでリーダーの1社の位置付けと評価された理由をご確認ください。
              ダミーのためのジェネレーティブAIの保護
              ダミーのためのジェネレーティブAIの保護
              Learn how your organization can balance the innovative potential of generative AI with robust data security practices.
                Modern data loss prevention (DLP) for Dummies eBook
                最新の情報漏えい対策(DLP)for Dummies
                Get tips and tricks for transitioning to a cloud-delivered DLP.
                  SASEダミーのための最新のSD-WAN ブック
                  Modern SD-WAN for SASE Dummies
                  遊ぶのをやめる ネットワークアーキテクチャに追いつく
                    リスクがどこにあるかを理解する
                    Advanced Analytics transforms the way security operations teams apply data-driven insights to implement better policies. With Advanced Analytics, you can identify trends, zero in on areas of concern and use the data to take action.
                        レガシーVPNを完全に置き換えるための6つの最も説得力のあるユースケース
                        レガシーVPNを完全に置き換えるための6つの最も説得力のあるユースケース
                        Netskope One Private Access is the only solution that allows you to retire your VPN for good.
                          Colgate-Palmoliveは、スマートで適応性のあるデータ保護により「知的財産」を保護します
                          Colgate-Palmoliveは、スマートで適応性のあるデータ保護により「知的財産」を保護します
                            Netskope GovCloud
                            NetskopeがFedRAMPの高認証を達成
                            政府機関の変革を加速するには、Netskope GovCloud を選択してください。
                              Let's Do Great Things Together
                              Netskopeのパートナー中心の市場開拓戦略により、パートナーは企業のセキュリティを変革しながら、成長と収益性を最大化できます。
                                Netskopeソリューション
                                Netskope Cloud Exchange
                                Netskope Cloud Exchange (CE) provides customers with powerful integration tools to leverage investments across their security posture.
                                  Netskopeテクニカルサポート
                                  Netskopeテクニカルサポート
                                  クラウドセキュリティ、ネットワーキング、仮想化、コンテンツ配信、ソフトウェア開発など、多様なバックグラウンドを持つ全世界にいる有資格のサポートエンジニアが、タイムリーで質の高い技術支援を行っています。
                                    Netskopeの動画
                                    Netskopeトレーニング
                                    Netskopeのトレーニングは、クラウドセキュリティのエキスパートになるためのステップアップに活用できます。Netskopeは、お客様のデジタルトランスフォーメーションの取り組みにおける安全確保、そしてクラウド、Web、プライベートアプリケーションを最大限に活用するためのお手伝いをいたします。

                                      RedLine Stealer Campaign Abusing Discord via PDF Links

                                      Oct 03 2022

                                      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.

                                      Phishing email that delivers RedLine.

                                      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.

                                      PDF Redirecting the user to a Discord URL, which downloads RedLine.

                                      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.

                                      Older versions of the same PDF file containing different URLs.

                                      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.

                                      RedLine Stealer payload

                                      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
                                      Blocklisted countries by RedLine Stealer.

                                      RedLine Stealer is able to steal sensitive information from specific apps, such as Discord and Steam, as well as from browsers and FTP and VPN clients.

                                      RedLine searching for Discord Tokens.

                                      Furthermore, the latest version of RedLine is also able to steal data from cryptocurrency extensions on Google Chrome.

                                      RedLine Stealer searching for Google Chrome extensions related to cryptocurrency.

                                      This is the list of targeted Google Chrome extensions found in this specific sample:

                                      • AtomicWallet
                                      • Authenticator
                                      • BinanceChain
                                      • BitAppWallet
                                      • BoltX
                                      • BraveWallet
                                      • Coin98Wallet
                                      • Coinbase
                                      • EqualWallet
                                      • GuardaWallet
                                      • GuildWallet
                                      • HarmonyWallet
                                      • iWallet
                                      • JaxxxLiberty
                                      • KardiaChain
                                      • LiqualityWallet
                                      • MaiarDeFiWallet
                                      • MathWallet
                                      • Metamask
                                      • MewCx
                                      • NamiWallet
                                      • NiftyWallet
                                      • Oxygen
                                      • PaliWallet
                                      • Phantom
                                      • RoninWallet
                                      • SaturnWallet
                                      • TempleWallet
                                      • TerraStation
                                      • TonCrystal
                                      • Tronlink
                                      • Wombat
                                      • XdefiWallet
                                      • YoroiWallet

                                      Lastly, we can find the RedLine Stealer C2 server and ID encrypted in its configuration. The data is base64 encoded and encrypted with a simple XOR algorithm using “Unhandier” as key.

                                      RedLine Stealer configuration.

                                      The decrypted C2 server address can be found in our GitHub repository.

                                      Older versions of the same PDF

                                      As previously mentioned, we found three additional URLs by analyzing the update history of the PDF. At the time of the analysis, all the URLs were still online and downloading other malware. 

                                      Unlike RedLine Stealer, these other URLs were not downloading the final payload directly. Instead, they are downloading an HTA file (either directly or compressed) which is responsible for downloading and executing a payload, also hosted on Discord.

                                      The first version of the PDF downloads a RAR file (“Invoice_NO355449609.rar”) with a compressed HTA file, which contains a Visual Basic Script that downloads the next stage payload (“Server.exe”) from Discord using bitsadmin.

                                      First version of the PDF downloading a different malware.

                                      The downloaded file (“Server.exe”) is NjRAT, which is a remote access trojan first spotted somewhere between 2013 and 2014.

                                      NjRAT payload details.

                                      This trojan provides remote access to infected machines, offering many functionalities such as access to the victim’s webcam, stealing credentials stored on browsers, and stealing keystrokes.

                                      Part of NjRAT keylogger functionality.

                                      Although this is not configured for this specific binary, there’s a feature that searches for Bitcoin addresses in the victim’s clipboard and replaces the value with the attacker’s address.

                                      Feature to steal Bitcoins by replacing addresses in the clipboard.

                                      This NjRAT payload is version 0.7d and it injects itself into a “svchost.exe” process.

                                      NjRAT configuration variables.

                                      The second and third version of the PDF works similarly to the first version, by downloading and executing an HTA file from Discord. The only difference between these versions is that the third one downloads the HTA file within a RAR (“Encrypted.rar”).

                                      Second and third version of the PDF downloading another malware from Discord.

                                      The downloaded file (“system.exe”) is PureCrypter, which is a malware loader commonly used to deliver other malware such as RedLine Stealer, AgentTesla, AsyncRAT, and others.

                                      PureCrypter binary details.

                                      This is a multi-stage malware that first runs PowerShell to sleep for 15 seconds and then loads the next stage from its own resources, which are compressed with gzip.

                                      First stage of PureCrypter.

                                      The next stage is highly obfuscated. Once running, it loads and decrypts a file from its resources using AES, which is a resource-only .NET binary that contains the final payload, which seems to be AgentTesla.

                                      Second stage of PureCrypter loading the next payload.

                                      Conclusions

                                      Attackers commonly target individuals with cheap remote access trojans, like RedLine Stealer, which can be found in underground forums for about $100 USD. Although these are simple attacks given the delivery method and types of malware, these kinds of threats can cause serious damage to individuals by stealing sensitive information, such as credit card numbers, website accounts, or cryptocurrency wallets. We strongly recommend individuals  avoid opening unknown files or clicking unknown links, especially if those were received by email. Also, using an antivirus endpoint solution could help as these are well known malware families.

                                      Protection

                                      Netskope Threat Labs is actively monitoring this campaign and has ensured coverage for all known threat indicators and payloads. 

                                      • Netskope Threat Protection
                                        • Win32.Trojan.RedLineStealer
                                        • Win32.Infostealer.RedLine
                                        • ByteCode-MSIL.Backdoor.Bladabhindi
                                        • ByteCode-MSIL.Trojan.AgentTesla
                                      • Netskope Advanced Threat Protection provides proactive coverage against this threat.
                                        • Gen.Malware.Detect.By.StHeur indicates a sample that was detected using static analysis
                                        • Gen.Malware.Detect.By.Sandbox indicates a sample that was detected by our cloud sandbox

                                      IOCs

                                      All the IOCs related to this campaign, scripts, and the Yara rules can be found in our GitHub repository.

                                      author image
                                      Gustavo Palazolo
                                      Gustavo Palazolo is an expert in malware analysis, reverse engineering and security research, working many years in projects related to electronic fraud protection.
                                      Gustavo Palazolo is an expert in malware analysis, reverse engineering and security research, working many years in projects related to electronic fraud protection.

                                      Stay informed!

                                      Subscribe for the latest from the Netskope Blog