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AIがランサムウェアから重要インフラを保護







2021年のRSAサイバーセキュリティカンファレンスにおいて、米国国土安全保障長官アレハンドロ・マヨルカス氏から、サイバーセキュリティ環境についてこの時代を定義する発言がありました:「はっきり言います。ランサムウェアは今や国家安全保障上の危機です。」
先週末、マヨルカス長官の言葉は現実となりました。米国東海岸のディーゼル、ガソリン、ジェット燃料の半分近くを担うColonial Pipelineに対するランサムウェア攻撃は、東海岸の多くの州に供給する重要な燃料ネットワークのシャットダウンを招きました。
この攻撃の影響は、ランサムウェアの結果がどれほど広範で被害の大きいものとなるかを証明しました。重要インフラに対し、サイバー攻撃は供給を中断し、環境を破壊し、場合によっては人命にかかわる危険性も持っています。
詳細な情報はまだ確認されていない部分もありますが、この攻撃はDarkSideと呼ばれるサイバー犯罪者の関連組織が実行したものと報じられており、おそらく一般的なリモートデスクトップツールを使ったとされています。リモートアクセスは、ICS(Industrial Control SystemsおよびOT(Operational Technology)を含む多くの組織が昨年行ったリモートワークへのシフトにより、重要インフラ内の悪用可能な脆弱性となりました。
産業用ランサムウェアの台頭
産業用環境を標的としたランサムウェアは増えつつあり、2018年以降に500%増加していると報告されています。多くの場合、これらの脅威はITとOTの統合を利用し、まずITを標的としてからOTに転回していきます。ICSプロセスを「キルリスト」に含めていたEKANSランサムウェア、ならびに最初にVPN(Virtual Private Network)の脆弱性を悪用してからICSに侵入したCring ランサムウェアでもそうした様子が見られました。
Colonial Pipelineへの侵害の最初の攻撃ベクトルが技術的な脆弱性をエクスプロイトしたものか、認証情報の流出があったのか、あるいは標的型スピアフィッシングであったのかはまだ明らかになっていません。攻撃は最初にITシステムに影響し、安全のための予防措置としてColonialがOTオペレーションをシャットダウンしたということが報じられています。Colonial はランサムウェアが「一時的にすべてのパイプライン操業を停止させ、ITシステムの一部に影響した」ことを確認しており、最終的にOTとITの両方が影響を受けたことがわかります。これは多くのOTシステムがITシステムに依存しており、ITサイバー攻撃がOTやICSプロセスをダウンさせることができるということを非常によく表している例です。
システムをダウンさせることに加えて、脅威アクターはColonialから100GBもの機密データを盗みました。ファイルの暗号化前にデータ抜き出しが行われるというこの種の二重恐喝攻撃は、残念ながら例外というよりも標準となっており、ランサムウェア攻撃の70%以上にはデータ抜き出しも含まれています。一部のランサムウェアギャングは暗号化を丸ごと放棄して、データ盗み出しと恐喝の手法を選択しています。
今年初め、Darktraceは重要インフラ企業に対する二重恐喝ランサムウェア攻撃を阻止しましたが、これには一般的なリモートアクセスツールが使用されていました。このブログでは発見された脅威を詳しく解説し、Darktraceの自己学習型AIがColonial Pipeline インシデントに非常によく似た攻撃に自律的に対処した事例を紹介します。
Darktraceによる脅威の発見
電力機器サプライヤーを標的としたランサムウェア
今年初めに発生した北米の電力機器サプライヤーに対する攻撃において、 DarktraceのIndustrial Immune Systemは、ICSとOTを持つ組織を標的とした二重恐喝ランサムウェアから重要インフラを保護する能力を実証しました。
このランサムウェアは最初にITシステムを標的としましたが、自己学習型Cyber AIにより、OTシステムに拡大し業務を中断させる前に阻止されました。
12時間の間に、攻撃者はまず内部サーバーに侵入し、データを盗み出してランサムウェアを展開しようとしました。最初の侵入から展開までの時間が短いことは珍しいと言えます。ランサムウェア脅威アクターは多くの場合、できるだけ目立たずに数日間かけてサイバーエコシステム内を可能な限り広範囲に拡散してから攻撃するからです。

図1: 攻撃のタイムライン
攻撃は他のセキュリティスタックをどのようにすり抜けたか?
攻撃者は ‘Living off the Land’ (環境に寄生する)テクニックでこの会社の通常の「生活パターン」に溶け込もうとしました。盗んだ管理者認証情報と会社で認められたリモート管理ツールを使い、検知を免れようとしたのです。
Darktraceは正統なリモート管理ソフトウェアが攻撃者のTTP(戦術、テクニック、手順)で悪用される事例を数多く観測しています。リモートアクセスは特にICS攻撃において一般的になりつつある攻撃ベクトルでもあります。たとえば、2月に発生したフロリダ州の水処理施設で発生したサイバーインシデントでは、攻撃者はリモート管理ツールを使って水処理のプロセスを操作しようとしました。
この攻撃者が使った種類のランサムウェアは、ファイルを暗号化する際独自のファイル拡張子を使うことによってアンチウィルスソフトの検知を回避することに成功しています。こうした形の「シグネチャのない」ランサムウェアは、ルール、シグネチャ、脅威フィード、およびCVE(Common Vulnerabilities and Exposures)リストに依存する従来のアプローチを簡単にすり抜けます。これらの手法は過去に文書化された脅威しか検知できないからです。
シグネチャのないランサムウェアなど以前に見られたことのない脅威を検知する唯一の方法は、「既知の悪」のリストに頼ることではなく、異常な動作を見つけることです。これは組織内のあらゆるデバイス、ユーザー、コントローラ、およびそれらの間のすべての接続についての通常の「生活パターン」からのごくわずかな逸脱も見つけることができる自己学習型テクノロジーによって可能になります。
Darktrace の考察
最初の侵入と足掛かりの確立
正統なツールが悪用され、既知のシグネチャが存在していなかったにもかかわらず、DarktraceのIndustrial Immune Systemは正常なアクティビティについてのホリスティックな理解を使用して悪意あるアクティビティを攻撃ライフサイクルの複数のポイントで検知することができました。
Darktraceがアラートした、脅威の発生を示す最初の明確な兆候は、特権的認証情報の不審な使用でした。このデバイスはさらに、インシデントの直前にVeeamサーバーから不審なRDP(Remote Desktop Protocol)接続を受けており、攻撃者がネットワークの別の場所から水平移動してきた可能性を示しています。
3分後、このデバイスはリモート管理セッションを開始し、それは21時間続きました。これにより攻撃者は従来型の防御からは検知されないまま、サイバーエコシステム内を幅広く移動することができました。しかし、Darktraceは攻撃を示すさらなる早期の前触れとして、この不審なリモート管理の使用を検知していました。
二重脅威パート1:データ抜き出し
最初の侵入から1時間後、Darktraceは不審な量のデータが100%未知のクラウドストレージソリューション、pCloudに送信されていることを検知しました。送信されたデータはSSLを使って暗号化されていましたが、Darktraceはこのデバイスの通常の「生活パターン」からの著しい逸脱である大量の内部ダウンロードおよび外部アップロードに関連して複数のアラートを生成しました。
デバイスは9時間に渡ってデータの抜き出しを続けました。このデバイスにより暗号化されていないSMBプロトコルを使ってダウンロードされたファイルを分析したところ、これらは機密性が高いものであることを示唆していました。幸いなことに、Darktraceは抜き出されたファイルをピンポイントで特定することができたため、顧客は侵害の潜在的影響を即座に評価することができました。
二重脅威パート2:ファイル暗号化
そのすぐ後、現地時間 01:49 に、侵害されたデバイスはSharePointバックアップ共有ドライブでファイルを暗号化し始めました。その後3.5時間に渡り、デバイスは13,000個以上のファイルを少なくとも20個のSMB共有上で暗号化しました。Darktraceは問題のデバイスに対して合計で23個のアラートを生成し、それらは24時間に生成されたすべてのアラートの48%を占めていました。
DarktraceのCyber AI Analystはその後自動的に調査を開始し、内部のファイル転送とSMB上のファイル暗号化を特定しました。ここからCyber AI Analystはインシデントレポートを作成し、個別の異常の点と点をつなぎ合わせ、これらを明快なセキュリティ上の経緯説明にまとめました。これにより、セキュリティチームは即座に是正のためのアクションを取る体制ができました。
この顧客がDarktraceの自動遮断テクノロジーであるDarktrace RESPONDを利用していれば、大量のデータが抜き出されたりファイルが暗号化されたりする前にこれらのアクティビティが阻止されていたことは疑いありません。幸い、アラートとCyber AI Analystのレポートを見たこの顧客はDarktraceのAsk the Expert (ATE) サービスを使って、攻撃の影響を緩和するためのインシデント対応と被害復旧についての支援を受けることができました。

図2:DarktraceのCyber AI Analystが検知した異常な暗号化とICS管理者接続の疑わしい一連の利用の例
重要インフラが停止させられる前に脅威を検知
標的となったサプライヤーはOTを管理しており重要インフラ分野に密接な関係を持っていました。早期段階での対応を促進することにより、Darktraceはランサムウェアが製造現場にまで拡散するのを防ぐことができました。重要な点として、Darktraceは業務の中断も最小化し、攻撃によって起こったかもしれないドミノ効果を避けることができました。攻撃によりこのサプライヤーだけでなく、サプライヤーがサポートする電力設備にも影響が及ぶ恐れがあったのです。
最近のColonial Pipelineインシデントや上記の脅威検知結果が示している通り、パイプラインから電力グリッドおよびそのサプライヤーに至るまで、あらゆる形態の重要インフラに対する産業用環境を管理している組織にとってランサムウェアは切実な悩みです。自己学習型AIにより、リアルタイムの脅威検知、自律的調査、そして有効に設定しておけば、的を絞ったマシンスピードの自動対処により、被害が出る前にこれらの脅威ベクトルに対して措置が可能です。
今後の展望:自己学習型AIを使ってあらゆる重要インフラを保護
4月下旬、バイデン政権は「米国の重要インフラを執拗かつ巧妙な脅威から保護する」ための野心的取り組みを発表しました。エネルギー省(DOE)の100日計画は、「電力サイバー可視性、検知、対処能力を電力事業の産業用制御システムに提供する」テクノロジーを求めています。
バイデン政権のサイバー計画は単なるベストプラクティス手法や規制ではなく、重要なエネルギーインフラを保護するテクノロジーを明確に求めています。上記の脅威事例でも確認されたように、Darktrace AIは教師なし機械学習を活用して重要インフラおよびそのサプライヤーをマシンのスピードおよび精度で自律的に保護する強力なテクノロジーです。
エネルギー省のサイバー計画目標
Darktraceの機能:検知、緩和、フォレンジック能力の強化、ルール、シグネチャ、CVEのリストを使わずに自己学習型Cyber AIにより、巧妙で新種の攻撃、および内部関係者からの脅威と既に存在していた感染を検知、Cyber AI Analyst によりリアルタイムに提供されるインシデント調査により、アクション可能な情報に基づいて即座に是正を開始、出現しつつある脅威が危機に発展する前に早期に封じ込める、重要なICS(Industrial Control System)およびOT(Operational Technology)においてリアルタイムに近い状況認識および対処機能を可能にするテクノロジーおよびシステムを導入する、自己学習型AIがICS/OTネットワーク内のあらゆる異常なアクティビティを、人間によるものかマシンによるものかを問わず即座に理解、識別および調査、能動的にあるいは人間が確認を行うモードにおいて、適切な場所に脅威を無害化するための的を絞った措置を実行、自己学習型AIはエコシステムの進化に適応し、微調整や人間による入力を必要とすることなくリアルタイムの認識を実現、重要インフラのITネットワークのセキュリティ体制を強化する、セキュリティイベントをコンテキスト化し、新手のテクニックに適応し、調査結果からセキュリティインシデントの経緯をまとめ、これによって数分で措置を取ることが可能、ITおよびOTシステムに対する統一された可視性、高次のPurdueレベルおよびITシステム内の脅威がOTに流れ込む前に検知、調査および対処、ICSおよびOTシステム内の脅威に対する可視性を高めるテクノロジーの導入、「プラグランドプレイ」環境によりテクノロジーアーキテクチャとシームレスに統合、あらゆるユーザー、デバイス、サブネットを細かいレベルで可視化した3Dネットワークトポロジーを提示、自己学習型アセット識別によりすべてのICS/OTデバイスを継続的にカタログ化、ICSランサムウェア、APT、ゼロデイエクスプロイト、内部関係者からの脅威、既に存在していた感染、DDoS、クリプトマイニング、設定のミス、これまで見られたことのない攻撃など、攻撃の発生を示すあらゆる脅威アクティビティを識別し調査
この脅威についての考察はDarktraceアナリストOakley Cox が協力しました。
Darktraceによるモデル検知:
- 最初の侵入:
- User / New Admin Credential on Client
- データ漏えい:
- Anomalous Connection / Uncommon 1 GiB Outbound
- Anomalous Connection / Low and Slow Exfiltration
- Device / Anomalous SMB Followed by Multiple Model Breaches
- Anomalous Connection / Download and Upload
- ファイル暗号化:
- Compromise / Ransomware / Suspicious SMB Activity
- Anomalous Connection / SMB Enumeration
- Device / Anomalous RDP Followed by Multiple Model Breaches
- Anomalous File / Internal / Additional Extension Appended to SMB File
- Anomalous Connection / Sustained MIME Type Conversion
- Anomalous Connection / Suspicious Read Write Ratio
- Device / Multiple Lateral Movement Model Breaches
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Inside the SOC
ViperSoftX: How Darktrace Uncovered A Venomous Intrusion



Fighting Info-Stealing Malware
The escalating threat posed by information-stealing malware designed to harvest and steal the sensitive data of individuals and organizations alike has become a paramount concern for security teams across the threat landscape. In direct response to security teams improving their threat detection and prevention capabilities, threat actors are forced to continually adapt and advance their techniques, striving for greater sophistication to ensure they can achieve the malicious goals.
What is ViperSoftX?
ViperSoftX is an information stealer and Remote Access Trojan (RAT) malware known to steal privileged information such as cryptocurrency wallet addresses and password information stored in browsers and password managers. It is commonly distributed via the download of cracked software from multiple sources such as suspicious domains, torrent downloads, and key generators (keygens) from third-party sites.
ViperSoftX was first observed in the wild in 2020 [1] but more recently, new strains were identified in 2022 and 2023 utilizing more sophisticated detection evasion techniques, making it more difficult for security teams to identify and analyze. This includes using more advanced encryption methods alongside monthly changes to command-and-control servers (C2) [2], using dynamic-link library (DLL) sideloading for execution techiques, and subsequently loading a malicious browser extension upon infection which works as an independent info-stealer named VenomSoftX [3].
Between February and June 2023, Darktrace detected activity related to the VipersoftX and VenomSoftX information stealers on the networks of more than 100 customers across its fleet. Darktrace DETECT™ was able to successfully identify the anomalous network activity surrounding these emerging information stealer infections and bring them to the attention of the customers, while Darktrace RESPOND™, when enabled in autonomous response mode, was able to quickly intervene and shut down malicious downloads and data exfiltration attempts.
ViperSoftX Attack & Darktrace Coverage
In cases of ViperSoftX information stealer activity observed by Darktrace, the initial infection was caused through the download of malicious files from multimedia sites, endpoints of cracked software like Adobe Illustrator, and torrent sites. Endpoint users typically unknowingly download the malware from these endpoints with a sideloaded DLL, posing as legitimate software executables.
Darktrace detected multiple downloads from such multimedia sites and endpoints related to cracked software and BitTorrent, which were likely representative of the initial source of ViperSoftX infection. Darktrace DETECT models such as ‘Anomalous File / Anomalous Octet Stream (No User Agent)’ breached in response to this activity and were brought to the immediate attention of customer security teams. In instances where Darktrace RESPOND was configured in autonomous response mode, Darktrace was able to enforce a pattern of life on offending devices, preventing them from downloading malicious files. This ensures that devices are limited to conducting only their pre-established expected activit, minimizing disruption to the business whilst targetedly mitigating suspicious file downloads.
The downloads are then extracted, decrypted and begin to run on the device. The now compromised device will then proceed to make external connections to C2 servers to retrieve secondary PowerShell executable. Darktrace identified that infected devices using PowerShell user agents whilst making HTTP GET requests to domain generation algorithm (DGA) ViperSoftX domains represented new, and therefore unusual, activity in a large number of cases.
For example, Darktrace detected one customer device making an HTTP GET request to the endpoint ‘chatgigi2[.]com’, using the PowerShell user agent ‘Mozilla/5.0 (Windows NT; Windows NT 10.0; en-US) WindowsPowerShell/5.1.19041.2364’. This new activity triggered a number of DETECT models, including ‘Anomalous Connection / PowerShell to Rare External’ and ‘Device / New PowerShell User Agent’. Repeated connections to these endpoints also triggered C2 beaconing models including:
- Compromise / Agent Beacon (Short Period)
- Compromise / Agent Beacon (Medium Period)
- Compromise / Agent Beacon (Long Period)
- Compromise / Quick and Regular Windows HTTP Beaconing
- Compromise / SSL or HTTP Beacon
Although a large number of different DGA domains were detected, commonalities in URI formats were seen across affected customers which matched formats previously identified as ViperSoftX C2 communication by open-source intelligence (OSINT), and in other Darktrace investigations.
URI paths for example, were always of the format /api/, /api/v1/, /v2/, or /v3/, appearing to detail version number, as can be seen in Figure 1.

Before the secondary PowerShell executables are loaded, ViperSoftX takes a digital fingerprint of the infected machine to gather its configuration details, and exfiltrates them to the C2 server. These include the computer name, username, Operating System (OS), and ensures there are no anti-virus or montoring tools on the device. If no security tool are detected, ViperSoftX then downloads, decrypts and executes the PowerShell file.
Following the GET requests Darktrace observed numerous devices performing HTTP POST requests and beaconing connections to ViperSoftX endpoints with varying globally unique identifiers (GUIDs) within the URIs. These connections represented the exfiltration of device configuration details, such as “anti-virus detected”, “app used”, and “device name”. As seen on another customer’s deployment, this caused the model ‘Anomalous Connection / Multiple HTTP POSTs to Rare Hostname’ to breach, which was also detected by Cyber AI Analyst as seen in Figure 2.

The malicious PowerShell download then crawls the infected device’s systems and directories looking for any cryptocurrency wallet information and password managers, and exfiltrates harvest data to the C2 infrastructure. The C2 server then provides further browser extensions to Chromium browsers to be downloaded and act as a separate stand-alone information stealer, also known as VenomSoftX.
Similar to the initial download of ViperSoftX, these malicious extensions are disguised as legitimate browser extensions to evade the detection of security teams. VenomSoft X, in turn, searches through and attempts to gather sensitive data from password managers and crypto wallets stored in user browsers. Using this information, VenomSoftX is able to redirect crypocurrency transactions by intercepting and manipulating API requests between the sender and the intended recipient, directing the cryptocurrency to the attacker instead [3].
Following investigation into VipersoftX activity across the customer base, Darktrace notified all affected customers and opened Ask the Expert (ATE) tickets through which customer’s could directly contact the analyst team for support and guidance in the face on the information stealer infection.
攻撃は他のセキュリティスタックをどのようにすり抜けたか?
As previously mentioned, both the initial download of ViperSoftX and the subsequent download of the VenomX browser extension are disguised as legitimate software or browser downloads. This is a common technique employed by threat actors to infect target devices with malicious software, while going unnoticed by security teams traditional security measures. Furthermore, by masquerading as a legitimate piece of software endpoint users are more likely to trust and therefore download the malware, increasing the likelihood of threat actor’s successfully carrying out their objectives. Additionally, post-infection analysis of shellcode, the executable code used as the payload, is made significantly more difficult by VenomSoftX’s use of bytemapping. Bytemapping prevents the encryption of shellcodes without its corresponding byte map, meaning that the payloads cannot easily be decrypted and analysed by security researchers. [3]
ViperSoftX also takes numerous attempts to prevent their C2 infrastructure from being identified by blocking access to it on browsers, and using multiple DGA domains, thus renderring defunct traditional security measures that rely on threat intelligence and static lists of indicators of compromise (IoCs).
Fortunately for Darktrace customers, Darktrace’s anomaly-based approach to threat detection means that it was able to detect and alert customers to this suspicious activity that may have gone unnoticed by other security tools.
Insights/Conclusion
Faced with the challenge of increasingly competent and capable security teams, malicious actors are having to adopt more sophisticated techniques to successfully compromise target systems and achieve their nefarious goals.
ViperSoftX information stealer makes use of numerous tactics, techniques and procedures (TTPs) designed to fly under the radar and carry out their objectives without being detected. ViperSoftX does not rely on just one information stealing malware, but two with the subsequent injection of the VenomSoftX browser extension, adding an additional layer of sophistication to the informational stealing operation and increasing the potential yield of sensitive data. Furthermore, the use of evasion techniques like disguising malicious file downloads as legitimate software and frequently changing DGA domains means that ViperSoftX is well equipped to infiltrate target systems and exfiltrate confidential information without being detected.
However, the anomaly-based detection capabilities of Darktrace DETECT allows it to identify subtle changes in a device’s behavior, that could be indicative of an emerging compromise, and bring it to the customer’s security team. Darktrace RESPOND is then autonomously able to take action against suspicious activity and shut it down without latency, minimizing disruption to the business and preventing potentially significant financial losses.
Credit to: Zoe Tilsiter, Senior Cyber Analyst, Nathan Lorenzo, Cyber Analyst.
付録
参考文献
[1] https://www.fortinet.com/blog/threat-research/vipersoftx-new-javascript-threat
[2] https://www.trendmicro.com/en_us/research/23/d/vipersoftx-updates-encryption-steals-data.html
[3] https://decoded.avast.io/janrubin/vipersoftx-hiding-in-system-logs-and-spreading-venomsoftx/
Darktrace DETECT Model Detections
· Anomalous File / Anomalous Octet Stream (No User Agent)
· Anomalous Connection / PowerShell to Rare External
· Anomalous Connection / Multiple HTTP POSTs to Rare Hostname
· Anomalous Connection / Lots of New Connections
· Anomalous Connection / Multiple Failed Connections to Rare Endpoint
· Anomalous Server Activity / Outgoing from Server
· Compromise / Large DNS Volume for Suspicious Domain
· Compromise / Quick and Regular Windows HTTP Beaconing
· Compromise / Beacon for 4 Days
· Compromise / Suspicious Beaconing Behaviour
· Compromise / Large Number of Suspicious Failed Connections
· Compromise / Large Number of Suspicious Successful Connections
· Compromise / POST and Beacon to Rare External
· Compromise / DGA Beacon
· Compromise / Agent Beacon (Long Period)
· Compromise / Agent Beacon (Medium Period)
· Compromise / Agent Beacon (Short Period)
· Compromise / Fast Beaconing to DGA
· Compromise / SSL or HTTP Beacon
· Compromise / Slow Beaconing Activity To External Rare
· Compromise / Beaconing Activity To External Rare
· Compromise / Excessive Posts to Root
· Compromise / Connections with Suspicious DNS
· Compromise / HTTP Beaconing to Rare Destination
· Compromise / High Volume of Connections with Beacon Score
· Compromise / Sustained SSL or HTTP Increase
· Device / New PowerShell User Agent
· Device / New User Agent and New IP
Darktrace RESPOND Model Detections
· Antigena / Network / External Threat / Antigena Suspicious File Block
· Antigena / Network / External Threat / Antigena File then New Outbound Block
· Antigena / Network / External Threat / Antigena Watched Domain Block
· Antigena / Network / Significant Anomaly / Antigena Significant Anomaly from Client Block
· Antigena / Network / External Threat / Antigena Suspicious Activity Block
· Antigena / Network / Significant Anomaly / Antigena Breaches Over Time Block
· Antigena / Network / Insider Threat / Antigena Large Data Volume Outbound Block
· Antigena / Network / External Threat / Antigena Suspicious File Pattern of Life Block
· Antigena / Network / Significant Anomaly / Antigena Controlled and Model Breach
IoC一覧
Indicator - Type - Description
ahoravideo-blog[.]com - Hostname - ViperSoftX C2 endpoint
ahoravideo-blog[.]xyz - Hostname - ViperSoftX C2 endpoint
ahoravideo-cdn[.]com - Hostname - ViperSoftX C2 endpoint
ahoravideo-cdn[.]xyz - Hostname - ViperSoftX C2 endpoint
ahoravideo-chat[.]com - Hostname - ViperSoftX C2 endpoint
ahoravideo-chat[.]xyz - Hostname - ViperSoftX C2 endpoint
ahoravideo-endpoint[.]xyz - Hostname - ViperSoftX C2 endpoint
ahoravideo-schnellvpn[.]com - Hostname - ViperSoftX C2 endpoint
ahoravideo-schnellvpn[.]xyz - Hostname - ViperSoftX C2 endpoint
apibilng[.]com - Hostname - ViperSoftX C2 endpoint
arrowlchat[.]com - Hostname - ViperSoftX C2 endpoint
bideo-blog[.]com - Hostname - ViperSoftX C2 endpoint
bideo-blog[.]xyz - Hostname - ViperSoftX C2 endpoint
bideo-cdn[.]com - Hostname - ViperSoftX C2 endpoint
bideo-cdn[.]xyz - Hostname - ViperSoftX C2 endpoint
bideo-chat[.]com - Hostname - ViperSoftX C2 endpoint
bideo-chat[.]xyz - Hostname - ViperSoftX C2 endpoint
bideo-endpoint[.]com - Hostname - ViperSoftX C2 endpoint
bideo-endpoint[.]xyz - Hostname - ViperSoftX C2 endpoint
bideo-schnellvpn[.]com - Hostname - ViperSoftX C2 endpoint
chatgigi2[.]com - Hostname - ViperSoftX C2 endpoint
counter[.]wmail-service[.]com - Hostname - ViperSoftX C2 endpoint
fairu-cdn[.]xyz - Hostname - ViperSoftX C2 endpoint
fairu-chat[.]xyz - Hostname - ViperSoftX C2 endpoint
fairu-endpoint[.]com - Hostname - ViperSoftX C2 endpoint
fairu-schnellvpn[.]com - Hostname - ViperSoftX C2 endpoint
fairu-schnellvpn[.]xyz - Hostname - ViperSoftX C2 endpoint
privatproxy-blog[.]com - Hostname - ViperSoftX C2 endpoint
privatproxy-blog[.]xyz - Hostname - ViperSoftX C2 endpoint
privatproxy-cdn[.]com - Hostname - ViperSoftX C2 endpoint
privatproxy-cdn[.]xyz - Hostname - ViperSoftX C2 endpoint
privatproxy-endpoint[.]xyz - Hostname - ViperSoftX C2 endpoint
privatproxy-schnellvpn[.]com - Hostname - ViperSoftX C2 endpoint
privatproxy-schnellvpn[.]xyz - Hostname - ViperSoftX C2 endpoint
static-cdn-349[.]net - Hostname - ViperSoftX C2 endpoint
wmail-blog[.]com - Hostname - ViperSoftX C2 endpoint
wmail-cdn[.]xyz - Hostname - ViperSoftX C2 endpoint
wmail-chat[.]com - Hostname - ViperSoftX C2 endpoint
wmail-schnellvpn[.]com - Hostname - ViperSoftX C2 endpoint
wmail-schnellvpn[.]xyz - Hostname - ViperSoftX C2 endpoint
Mozilla/5.0 (Windows NT; Windows NT 10.0; en-US) WindowsPowerShell/5.1.19041.2364 - User Agent -PowerShell User Agent
MITRE ATT&CK マッピング
Tactic - Technique - Notes
Command and Control - T1568.002 Dynamic Resolution: Domain Generation Algorithms
Command and Control - T1321 Data Encoding
Credential Access - T1555.005 Credentials from Password Stores: Password Managers
Defense Evasion - T1027 Obfuscated Files or Information
Execution - T1059.001 Command and Scripting Interpreter: PowerShell
Execution - T1204 User Execution T1204.002 Malicious File
Persistence - T1176 Browser Extensions - VenomSoftX specific
Persistence, Privilege Escalation, Defense Evasion - T1574.002 Hijack Execution Flow: DLL Side-Loading
Blog
Inside the SOC
Protecting Prospects: How Darktrace Detected an Account Hijack Within Days of Deployment



Cloud Migration Expanding the Attack Surface
Cloud migration is here to stay – accelerated by pandemic lockdowns, there has been an ongoing increase in the use of public cloud services, and Gartner has forecasted worldwide public cloud spending to grow around 20%, or by almost USD 600 billion [1], in 2023. With more and more organizations utilizing cloud services and moving their operations to the cloud, there has also been a corresponding shift in malicious activity targeting cloud-based software and services, including Microsoft 365, a prominent and oft-used Software-as-a-Service (SaaS).
With the adoption and implementation of more SaaS products, the overall attack surface of an organization increases – this gives malicious actors additional opportunities to exploit and compromise a network, necessitating proper controls to be in place. This increased attack surface can leave organization’s open to cyber risks like cloud misconfigurations, supply chain attacks and zero-day vulnerabilities [2]. In order to achieve full visibility over cloud activity and prevent SaaS compromise, it is paramount for security teams to deploy sophisticated security measures that are able to learn an organization’s SaaS environment and detect suspicious activity at the earliest stage.
Darktrace Immediately Detects Hijacked Account
In May 2023, Darktrace observed a chain of suspicious SaaS activity on the network of a customer who was about to begin their trial of Darktrace/Cloud™ and Darktrace/Email™. Despite being deployed on the network for less than a week, Darktrace DETECT™ recognized that the legitimate SaaS account, belonging to an executive at the organization, had been hijacked. Darktrace/Email was able to provide full visibility over inbound and outbound mail and identified that the compromised account was subsequently used to launch an internal spear-phishing campaign.
If Darktrace RESPOND™ were enabled in autonomous response mode at the time of this compromise, it would have been able to take swift preventative action to disrupt the account compromise and prevent the ensuing phishing attack.
Account Hijack Attack Overview
Unusual External Sources for SaaS Credentials
On May 9, 2023, Darktrace DETECT/Cloud detected the first in a series of anomalous activities performed by a Microsoft 365 user account that was indicative of compromise, namely a failed login from an external IP address located in Virginia.

Just a few minutes later, Darktrace observed the same user credential being used to successfully login from the same unusual IP address, with multi-factor authentication (MFA) requirements satisfied.

A few hours after this, the user credential was once again used to login from a different city in the state of Virginia, with MFA requirements successfully met again. Around the time of this activity, the SaaS user account was also observed previewing various business-related files hosted on Microsoft SharePoint, behavior that, taken in isolation, did not appear to be out of the ordinary and could have represented legitimate activity.
The following day, May 10, however, there were additional login attempts observed from two different states within the US, namely Texas and Florida. Darktrace understood that this activity was extremely suspicious, as it was highly improbable that the legitimate user would be able to travel over 2,500 miles in such a short period of time. Both login attempts were successful and passed MFA requirements, suggesting that the malicious actor was employing techniques to bypass MFA. Such MFA bypass techniques could include inserting malicious infrastructure between the user and the application and intercepting user credentials and tokens, or by compromising browser cookies to bypass authentication controls [3]. There have also been high-profile cases in the recent years of legitimate users mistakenly (and perhaps even instinctively) accepting MFA prompts on their token or mobile device, believing it to be a legitimate process despite not having performed the login themselves.
New Email Rule
On the evening of May 10, following the successful logins from multiple US states, Darktrace observed the Microsoft 365 user creating a new inbox rule, named “.’, in Microsoft Outlook from an IP located in Florida. Threat actors are often observed naming new email rules with single characters, likely to evade detection, but also for the sake of expediency so as to not expend any additional time creating meaningful labels.
In this case the newly created email rules included several suspicious properties, including ‘AlwaysDeleteOutlookRulesBlob’, ‘StopProcessingRules’ and “MoveToFolder”.
Firstly, ‘AlwaysDeleteOutlookRulesBlob’ suppresses or hides warning messages that typically appear if modifications to email rules are made [4]. In this case, it is likely the malicious actor was attempting to implement this property to obfuscate the creation of new email rules.
The ‘StopProcessingRules’ rule meant that any subsequent email rules created by the legitimate user would be overridden by the email rule created by the malicious actor [5]. Finally, the implementation of “MoveToFolder” would allow the malicious actor to automatically move all outgoing emails from the “Sent” folder to the “Deleted Items” folder, for example, further obfuscating their malicious activities [6]. The utilization of these email rule properties is frequently observed during account hijackings as it allows attackers to delete and/or forward key emails, delete evidence of exploitation and launch phishing campaigns [7].
In this incident, the new email rule would likely have enabled the malicious actor to evade the detection of traditional security measures and achieve greater persistence using the Microsoft 365 account.

Account Update
A few hours after the creation of the new email rule, Darktrace observed the threat actor successfully changing the Microsoft 365 user’s account password, this time from a new IP address in Texas. As a result of this action, the attacker would have locked out the legitimate user, effectively gaining full access over the SaaS account.

Phishing Emails
The compromised SaaS account was then observed sending a high volume of suspicious emails to both internal and external email addresses. Darktrace was able to identify that the emails attempting to impersonate the legitimate service DocuSign and contained a malicious link prompting users to click on the text “Review Document”. Upon clicking this link, users would be redirected to a site hosted on Adobe Express, namely hxxps://express.adobe[.]com/page/A9ZKVObdXhN4p/.
Adobe Express is a free service that allows users to create web pages which can be hosted and shared publicly; it is likely that the threat actor here leveraged the service to use in their phishing campaign. When clicked, such links could result in a device unwittingly downloading malware hosted on the site, or direct unsuspecting users to a spoofed login page attempting to harvest user credentials by imitating legitimate companies like Microsoft.

The malicious site hosted on Adobe Express was subsequently taken down by Adobe, possibly in response to user reports of maliciousness. Unfortunately though, platforms like this that offer free webhosting services can easily and repeatedly be abused by malicious actors. Simply by creating new pages hosted on different IP addresses, actors are able to continue to carry out such phishing attacks against unsuspecting users.
In addition to the suspicious SaaS and email activity that took place between May 9 and May 10, Darktrace/Email also detected the compromised account sending and receiving suspicious emails starting on May 4, just two days after Darktrace’s initial deployment on the customer’s environment. It is probable that the SaaS account was compromised around this time, or even prior to Darktrace’s deployment on May 2, likely via a phishing and credential harvesting campaign similar to the one detailed above.

Darktrace のカバレッジ
As the customer was soon to begin their trial period, Darktrace RESPOND was set in “human confirmation” mode, meaning that any preventative RESPOND actions required manual application by the customer’s security team.
If Darktrace RESPOND had been enabled in autonomous response mode during this incident, it would have taken swift mitigative action by logging the suspicious user out of the SaaS account and disabling the account for a defined period of time, in doing so disrupting the attack at the earliest possible stage and giving the customer the necessary time to perform remediation steps. As it was, however, these RESPOND actions were suggested to the customer’s security team for them to manually apply.

Nevertheless, with Darktrace DETECT/Cloud in place, visibility over the anomalous cloud-based activities was significantly increased, enabling the swift identification of the chain of suspicious activities involved in this compromise.
In this case, the prospective customer reached out to Darktrace directly through the Ask the Expert (ATE) service. Darktrace’s expert analyst team then conducted a timely and comprehensive investigation into the suspicious activity surrounding this SaaS compromise, and shared these findings with the customer’s security team.
結論
Ultimately, this example of SaaS account compromise highlights Darktrace’s unique ability to learn an organization’s digital environment and recognize activity that is deemed to be unexpected, within a matter of days.
Due to the lack of obvious or known indicators of compromise (IoCs) associated with the malicious activity in this incident, this account hijack would likely have gone unnoticed by traditional security tools that rely on a rules and signatures-based approach to threat detection. However, Darktrace’s Self-Learning AI enables it to detect the subtle deviations in a device’s behavior that could be indicative of an ongoing compromise.
Despite being newly deployed on a prospective customer’s network, Darktrace DETECT was able to identify unusual login attempts from geographically improbable locations, suspicious email rule updates, password changes, as well as the subsequent mounting of a phishing campaign, all before the customer’s trial of Darktrace had even begun.
When enabled in autonomous response mode, Darktrace RESPOND would be able to take swift preventative action against such activity as soon as it is detected, effectively shutting down the compromise and mitigating any subsequent phishing attacks.
With the full deployment of Darktrace’s suite of products, including Darktrace/Cloud and Darktrace/Email, customers can rest assured their critical data and systems are protected, even in the case of hybrid and multi-cloud environments.
Credit: Samuel Wee, Senior Analyst Consultant & Model Developer
付録
参考文献
[2] https://www.upguard.com/blog/saas-security-risks
[4] https://learn.microsoft.com/en-us/powershell/module/exchange/disable-inboxrule?view=exchange-ps
[7] https://blog.knowbe4.com/check-your-email-rules-for-maliciousness
Darktraceによるモデル検知
Darktrace DETECT/Cloud and RESPOND Models Breached:
SaaS / Access / Unusual External Source for SaaS Credential Use
SaaS / Unusual Activity / Multiple Unusual External Sources for SaaS Credential
Antigena / SaaS / Antigena Unusual Activity Block (RESPOND Model)
SaaS / Compliance / New Email Rule
Antigena / SaaS / Antigena Significant Compliance Activity Block
SaaS / Compromise / Unusual Login and New Email Rule (Enhanced Monitoring Model)
Antigena / SaaS / Antigena Suspicious SaaS Activity Block (RESPOND Model)
SaaS / Compromise / SaaS Anomaly Following Anomalous Login (Enhanced Monitoring Model)
SaaS / Compromise / Unusual Login and Account Update
Antigena / SaaS / Antigena Suspicious SaaS Activity Block (RESPOND Model)
IoC – Type – Description & Confidence
hxxps://express.adobe[.]com/page/A9ZKVObdXhN4p/ - Domain – Probable Phishing Page (Now Defunct)
37.19.221[.]142 – IP Address – Unusual Login Source
35.174.4[.]92 – IP Address – Unusual Login Source
MITRE ATT&CK マッピング
Tactic - Techniques
INITIAL ACCESS, PRIVILEGE ESCALATION, DEFENSE EVASION, PERSISTENCE
T1078.004 – Cloud Accounts
探索
T1538 – Cloud Service Dashboards
CREDENTIAL ACCESS
T1539 – Steal Web Session Cookie
RESOURCE DEVELOPMENT
T1586 – Compromise Accounts
PERSISTENCE
T1137.005 – Outlook Rules
