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Qakbotの復活:新たな脅威の出現とともに進化

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30
Jan 2023
30
Jan 2023
2022 年 6 月、Darktrace は、そのクライアントベースで Qakbot 感染の急増を観察しました。これらの感染は、新しい配信方法によるものであるにもかかわらず、異常なパターンのネットワークトラフィックをもたらし、Darktrace/Networkはこれを検知し対応することができました。

2022年6月、Darktrace は同社のクライアントベースでQakbotの感染急増が確認しました。検知されたQakbotの感染は、場合によってはCobalt StrikeやDark VNCなどの2次ペイロードの配信につながり、2022年初頭にMicrosoftがXL4とVBAマクロをデフォルトでブロックしたこと[1]/[2]/[3]/[4]や、Microsoft Support Diagnostic Tool(MSDT)におけるFollina脆弱性の公開 [5] から生まれた新しい配信方式によって開始されたものでした。Qakbotの配信方法に変更が加えられたにもかかわらず、Qakbotの感染により、ネットワークアクティビティに異常なパターンが生じることは避けられませんでした。このブログでは、これらのネットワーク活動の詳細について、Darktrace/Networkのカバレッジ内容とともにご紹介します。 

Qakbotの背景 

Qakbotは、2007年に銀行の認証情報などの機密データを盗むために設計された銀行トロイの木馬として登場しました。 それ以来、Qakbotは、情報を盗むだけでなく、悪意のあるペイロードを投下し、バックドアとして機能する、高度にモジュール化された三拍子揃った脅威として発展しています。また、このマルウェアは汎用性が高く、脅威の変化に応じて配信方法も定期的に変更されています。  

脅威アクターは、Eメールベースの配信手法でQakbotを配信します。2022年前半、Microsoftは、XL4およびVBAマクロをデフォルトでブロックするバージョンのOfficeの展開を開始しました。この変更以前は、Qakbotのメールキャンペーンは、通常、悪意のあるマクロを含むOfficeの添付ファイルを含む詐欺的なメールの拡散で構成されていました。 これらの添付ファイルを開き、その中のマクロを有効にすることで、ユーザーのデバイスにQakbotがインストールされることになります。  

ユーザーのデバイスにQakbotを配信するアクターは、そのアクセス権を他のアクターに売却したり、Qakbotの機能を活用して独自の目的を追求したりすることがあります[6]。Qakbotを使用するアクターの共通の目的は、感染したシステム上にCobalt Strikeビーコンを投下することです。そして、脅威アクターは、Cobalt Strikeが提供するインタラクティブなアクセスを活用して、広範なランサムウェアの展開に備えた広範な偵察とラテラルムーブメントを行います。Qakbotは、そのモジュール性と汎用性に加え、ランサムウェアの活動と密接な関係があるため、組織のデジタル環境にとって重大な脅威となるマルウェアです。

活動の詳細とQakbotの配信方法

6月の1か月間、いくつかのクライアントネットワークにおいて、以下のようなネットワーク活動のバリエーションが観察されました。

1. ユーザーの端末がoutlook.office[.]com や mail.google[.]comなどのメールサービスにコンタクトを取る

2. ユーザーの端末が、185.234.247[.]119に対して、Officeユーザーエージェント文字列とターゲットURI「/123.RES」を指定してHTTP GETリクエストを実行し、このリクエストに対して、Follina脆弱性(CVE-2022-30190)を悪用したHTMLファイルが応答する

3. ユーザーのデバイスは、cURL User-Agent文字列と '.dat' で終わるターゲットURIを使用して、通常とは異なる外部エンドポイントにHTTP GETリクエストを実行し、このリクエストには、QakbotのDLLサンプルが応答する

4. ユーザーのデバイスが443、995、2222、32101などのポートを介してQakbot Command and Controlサーバーにコンタクトする

ステップ1と4だけが見える場合もあれば、ステップ1、3、4だけが見える場合もあります。このパターンの違いは、Qakbotの配信方法の違いに対応しています。

図1:Qakbotの影響を受けたDarktrace の顧客の地理的分布

Qakbotは、悪意のあるEメールの添付ファイルを介して配信されることが知られています [7]。6月中にDarktraceのクライアントベースで観測されたQakbotの感染は、HTMLの添付ファイルに悪意のあるコードを埋め込む手法であるHTMLスマグリングによって開始された可能性が高いと思われます。オープンソースのレポート [8]-[14] と観察されたネットワークトラフィックのパターンに基づき、2022年6月にDarktraceのクライアントベースで観察された Qakbot 感染は以下の3つの方法のいずれかによって開始されたと、中程度から高い信頼度で評価しています:

  • ユーザーはHTMLの添付ファイルを開き、ZIPファイルをデバイスにドロップします。ZIPファイルにはLNKファイルが含まれており、これを開くと、ユーザーのデバイスはcURLユーザーエージェント文字列とターゲットURI「.dat」を指定して外部HTTP GETリクエストを行います。成功すると、HTTP GETリクエストにQakbot DLLが応答します。
  • ユーザーはHTMLの添付ファイルを開き、ZIPファイルをユーザーのデバイスにドロップします。ZIPファイルにはdocxファイルが含まれており、これを開くと、ユーザーのデバイスは、Officeユーザーエージェント文字列と「/123.RES」ターゲットURIを持つ185.234.247[.] 119に対してHTTP GETリクエストを行います。成功すると、HTTP GETリクエストに対して、Follinaエクスプロイトを含むHTMLファイルが応答します。Follina エクスプロイトは、ユーザーのデバイスに、ターゲット URI が「.dat」である外部 HTTP GET を実行させるように仕向けます。成功すると、HTTP GET リクエストに Qakbot DL が応答します。
  • ユーザーがHTMLの添付ファイルを開くと、ZIPファイルがデバイスにドロップされます。ZIPファイルには、Qakbot DLLとLNKファイルが含まれており、開くとDLLが実行されます。

これらの配信方法は、マクロを埋め込んだOfficeドキュメントから、コンテナファイル、Windowsショートカット(LNK)ファイル、新しい脆弱性のエクスプロイトへと、マルウェア配信技術を変化させ、脅威アクターがポストマクロの世界にいかに適応しているかを示しています。[4] 

Darktraceのクライアントベースで観察されたQakbot感染は、その提供方法が異なるだけでなく、フォローアップ活動の点でも異なっていました。中には、フォローアップ活動が見られないケースもありました。しかし、Qakbotを利用してデータを流出させ、Cobalt StrikeやDark VNCといった後続のペイロードを配信しているケースも確認されています。これらのフォローアップ活動は、ランサムウェアを展開するための準備であると考えられます。Darktraceセキュリティチームは、クライアント環境内の Qakbot の活動を早期に検知することで、ランサムウェアの展開を防ぐことができたと思われる措置をとることができました。 

Darktrace のカバレッジ 

ユーザーが悪意のあるEメールの添付ファイルを使用した場合、通常、ユーザーの端末は、空のHostヘッダーと「.dat」で終わるターゲットURI(「/24736.dat」や「/noFindThem.dat」など)でcURL HTTP GETリクエストを、稀な外部のエンドポイントに送信することになりました。Follinaの脆弱性が悪用されたと考えられるケースでは、ユーザーの端末がcURLのHTTP GETリクエストを行う前に、Microsoft OfficeのUser Agent文字列を含む 185.234.247[.]119 にHTTP GETリクエストを行ったことが確認されています。これらのHTTPアクティビティの結果として典型的に侵入されたのは、以下のDarktrace DETECT/Networkモデルです。

  • Device / New User Agent
  • Anomalous Connection / New User Agent to IP Without Hostname
  • Device / New User Agent and New IP
  • Anomalous File / EXE from Rare External Location
  • Anomalous File / Numeric Exe Download 

これらのDETECT モデルは、影響を受けたデバイスにおけるOfficeとcURLのユーザーエージェント文字列の異常な使用と、稀な外部エンドポイントからのQakbot DLLのダウンロードを捕捉することが出来ました。これらのモデルは、悪意のあることが知られているユーザーエージェント文字列、URI、ファイル、および外部IPを含む活動ではなく、デバイスの通常の動作パターンから外れた異常な活動を探します。

有効化すると、Darktrace RESPOND/Networkが自律的に介入し、「グループの生活パターンを強制する」や 「接続をブロックする」などのアクションを取り、Qakbotインフラへの接続を迅速に遮断します。 

図2:この New User Agent to IP Without Hostname モデルブリーチは、Follinaエクスプロイトを含むファイルをダウンロードしようとするデバイスをDarktraceが検知した例を強調するものです
図3:この New User Agent to IP Without Hostname モデルブリーチは、QakbotをダウンロードしようとするデバイスのDarktrace「検知」の例を強調するものです
図4: 感染したデバイスのイベントログは、エンドポイントであるoutlook.office365[.]comへの接続が行われた瞬間を強調しています。この後、実行可能ファイル転送が検知され、新しいユーザーエージェントであるcurl/7.9.1が使用されました

Qakbotのインストール後、ユーザーのデバイスは443、22、990、995、1194、2222、2078、32101などのポート上でコマンド&コントロール(C2)エンドポイントに接続するようになりました。Cobalt StrikeとDark VNCは、これらのC2接続を介して配信された可能性があり、Cobalt StrikeとDark VNCに関連するエンドポイントへのその後の接続で証明されます。これらのC2活動は通常、以下のDarktrace DETECT/Networkモデルの侵害を引き起こしました。 

  • Anomalous Connection / Application Protocol on Uncommon Port
  • Anomalous Connection / Multiple Connections to New External TCP Port
  • Compromise / Suspicious Beaconing Behavior
  • Anomalous Connection / Multiple Failed Connections to Rare Endpoint
  • Compromise / Large Number of Suspicious Successful Connections
  • Compromise / Sustained SSL or HTTP Increase
  • Compromise / SSL or HTTP Beacon
  • Anomalous Connection / Rare External SSL Self-Signed
  • Anomalous Connection / Anomalous SSL without SNI to New External
  • Compromise / SSL Beaconing to Rare Destination
  • Compromise / Suspicious TLS Beaconing To Rare External
  • Compromise / Slow Beaconing Activity To External Rare
図5:このデバイスイベントログは、Qakbotに感染したデバイスが表示するCommand and Controlアクティビティを示しています

これらのC2活動を検知したDarktrace DETECT/Network モデルは、既知の悪意のあるエンドポイントに接続するデバイスを探すのではありません。むしろ、通常の活動パターンから逸脱し、内部デバイスが通常接続しない外部エンドポイントに、通常接続しないポートを介して接続するデバイスを探します。 

Qakbotに感染したシステムからデータを流出させ、Cobalt Strikeを投下して、大規模な調査を行うケースも確認されています。これらの侵入活動は、通常、以下のモデルの侵入を引き起こしました:

  • Anomalous Connection / Data Sent to Rare Domain
  • Unusual Activity / Enhanced Unusual External Data Transfer
  • Anomalous Connection / Uncommon 1 GiB Outbound
  • Anomalous Connection / Low and Slow Exfiltration to IP
  • Unusual Activity / Unusual External Data to New Endpoints

脅威アクターが行った偵察とブルートフォース活動は、通常、以下のモデルブリーチをもたらしました:

  • Device / ICMP Address Scan
  • Device / Network Scan
  • Anomalous Connection / SMB Enumeration
  • Device / New or Uncommon WMI Activity
  •  Unusual Activity / Possible RPC Recon Activity
  • Device / Possible SMB/NTLM Reconnaissance
  •  Device / SMB Lateral Movement
  •  Device / Increase in New RPC Services
  •  Device / Spike in LDAP Activity
  • Device / Possible SMB/NTLM Brute Force
  • Device / SMB Session Brute Force (Non-Admin)
  • Device / SMB Session Brute Force (Admin)
  • Device / Anomalous NTLM Brute Force

結論

2022年6月、Qakbotは、MicrosoftのマクロのデフォルトブロックとFollina脆弱性の一般公開に対応する形で迅速に自己形成しました。2022年前半の脅威の進化により、Qakbotは配信方法を変更し、マクロを使用した配信方法からHTMLスマグリングによる配信方法へと移行しました。これらの新しい配信方法の有効性は、2022年6月に大量のQakbot感染が確認されたDarktraceのクライアントベースで浮き彫りにされました。自己学習型AIを活用し、Darktrace DETECT/Networkは、これらの新しいQakbot感染から必然的に生じる異常なネットワーク挙動を検知することができました。これらのQakbot感染の背後にいるアクターはランサムウェアを展開しようとしていた可能性が高いことを考えると、これらの検知は、Darktrace RESPOND/Networkの自律的な介入とともに、最終的に影響を受けたDarktrace の顧客を重大なビジネスの混乱から保護するのに役立ちました。  

付録

IoC一覧

参考文献

[1] https://techcommunity.microsoft.com/t5/excel-blog/excel-4-0-xlm-macros-now-restricted-by-default-for-customer/ba-p/3057905

[2] https://techcommunity.microsoft.com/t5/microsoft-365-blog/helping-users-stay-safe-blocking-internet-macros-by-default-in/ba-p/3071805

[3] https://learn.microsoft.com/en-us/deployoffice/security/internet-macros-blocked

[4] https://www.proofpoint.com/uk/blog/threat-insight/how-threat-actors-are-adapting-post-macro-world

[5] https://twitter.com/nao_sec/status/1530196847679401984

[6] https://www.microsoft.com/security/blog/2021/12/09/a-closer-look-at-qakbots-latest-building-blocks-and-how-to-knock-them-down/

[7] https://www.zscaler.com/blogs/security-research/rise-qakbot-attacks-traced-evolving-threat-techniques

[8] https://www.esentire.com/blog/resurgence-in-qakbot-malware-activity

[9] https://www.fortinet.com/blog/threat-research/new-variant-of-qakbot-spread-by-phishing-emails

[10] https://twitter.com/pr0xylife/status/1539320429281615872

[11] https://twitter.com/max_mal_/status/1534220832242819072

[12] https://twitter.com/1zrr4h/status/1534259727059787783?lang=en

[13] https://isc.sans.edu/diary/rss/28728

[14] https://www.fortiguard.com/threat-signal-report/4616/qakbot-delivered-through-cve-2022-30190-follina

Credit to:  Hanah Darley, Cambridge Analyst Team Lead and Head of Threat Research and Sam Lister, Senior Cyber Analyst

INSIDE THE SOC
Darktrace cyber analysts are world-class experts in threat intelligence, threat hunting and incident response, and provide 24/7 SOC support to thousands of Darktrace customers around the globe. Inside the SOC is exclusively authored by these experts, providing analysis of cyber incidents and threat trends, based on real-world experience in the field.
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The State of AI in Cybersecurity: How AI will impact the cyber threat landscape in 2024

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22
Apr 2024

About the AI Cybersecurity Report

We surveyed 1,800 CISOs, security leaders, administrators, and practitioners from industries around the globe. Our research was conducted to understand how the adoption of new AI-powered offensive and defensive cybersecurity technologies are being managed by organizations.

This blog is continuing the conversation from our last blog post “The State of AI in Cybersecurity: Unveiling Global Insights from 1,800 Security Practitioners” which was an overview of the entire report. This blog will focus on one aspect of the overarching report, the impact of AI on the cyber threat landscape.

To access the full report click here.

Are organizations feeling the impact of AI-powered cyber threats?

Nearly three-quarters (74%) state AI-powered threats are now a significant issue. Almost nine in ten (89%) agree that AI-powered threats will remain a major challenge into the foreseeable future, not just for the next one to two years.

However, only a slight majority (56%) thought AI-powered threats were a separate issue from traditional/non AI-powered threats. This could be the case because there are few, if any, reliable methods to determine whether an attack is AI-powered.

Identifying exactly when and where AI is being applied may not ever be possible. However, it is possible for AI to affect every stage of the attack lifecycle. As such, defenders will likely need to focus on preparing for a world where threats are unique and are coming faster than ever before.

a hypothetical cyber attack augmented by AI at every stage

Are security stakeholders concerned about AI’s impact on cyber threats and risks?

The results from our survey showed that security practitioners are concerned that AI will impact organizations in a variety of ways. There was equal concern associated across the board – from volume and sophistication of malware to internal risks like leakage of proprietary information from employees using generative AI tools.

What this tells us is that defenders need to prepare for a greater volume of sophisticated attacks and balance this with a focus on cyber hygiene to manage internal risks.

One example of a growing internal risks is shadow AI. It takes little effort for employees to adopt publicly-available text-based generative AI systems to increase their productivity. This opens the door to “shadow AI”, which is the use of popular AI tools without organizational approval or oversight. Resulting security risks such as inadvertent exposure of sensitive information or intellectual property are an ever-growing concern.

Are organizations taking strides to reduce risks associated with adoption of AI in their application and computing environment?

71.2% of survey participants say their organization has taken steps specifically to reduce the risk of using AI within its application and computing environment.

16.3% of survey participants claim their organization has not taken these steps.

These findings are good news. Even as enterprises compete to get as much value from AI as they can, as quickly as possible, they’re tempering their eager embrace of new tools with sensible caution.

Still, responses varied across roles. Security analysts, operators, administrators, and incident responders are less likely to have said their organizations had taken AI risk mitigation steps than respondents in other roles. In fact, 79% of executives said steps had been taken, and only 54% of respondents in hands-on roles agreed. It seems that leaders believe their organizations are taking the needed steps, but practitioners are seeing a gap.

Do security professionals feel confident in their preparedness for the next generation of threats?

A majority of respondents (six out of every ten) believe their organizations are inadequately prepared to face the next generation of AI-powered threats.

The survey findings reveal contrasting perceptions of organizational preparedness for cybersecurity threats across different regions and job roles. Security administrators, due to their hands-on experience, express the highest level of skepticism, with 72% feeling their organizations are inadequately prepared. Notably, respondents in mid-sized organizations feel the least prepared, while those in the largest companies feel the most prepared.

Regionally, participants in Asia-Pacific are most likely to believe their organizations are unprepared, while those in Latin America feel the most prepared. This aligns with the observation that Asia-Pacific has been the most impacted region by cybersecurity threats in recent years, according to the IBM X-Force Threat Intelligence Index.

The optimism among Latin American respondents could be attributed to lower threat volumes experienced in the region, but it's cautioned that this could change suddenly (1).

What are biggest barriers to defending against AI-powered threats?

The top-ranked inhibitors center on knowledge and personnel. However, issues are alluded to almost equally across the board including concerns around budget, tool integration, lack of attention to AI-powered threats, and poor cyber hygiene.

The cybersecurity industry is facing a significant shortage of skilled professionals, with a global deficit of approximately 4 million experts (2). As organizations struggle to manage their security tools and alerts, the challenge intensifies with the increasing adoption of AI by attackers. This shift has altered the demands on security teams, requiring practitioners to possess broad and deep knowledge across rapidly evolving solution stacks.

Educating end users about AI-driven defenses becomes paramount as organizations grapple with the shortage of professionals proficient in managing AI-powered security tools. Operationalizing machine learning models for effectiveness and accuracy emerges as a crucial skill set in high demand. However, our survey highlights a concerning lack of understanding among cybersecurity professionals regarding AI-driven threats and the use of AI-driven countermeasures indicating a gap in keeping pace with evolving attacker tactics.

The integration of security solutions remains a notable problem, hindering effective defense strategies. While budget constraints are not a primary inhibitor, organizations must prioritize addressing these challenges to bolster their cybersecurity posture. It's imperative for stakeholders to recognize the importance of investing in skilled professionals and integrated security solutions to mitigate emerging threats effectively.

To access the full report click here.

参考文献

1. IBM, X-Force Threat Intelligence Index 2024, Available at: https://www.ibm.com/downloads/cas/L0GKXDWJ

2. ISC2, Cybersecurity Workforce Study 2023, Available at: https://media.isc2.org/-/media/Project/ISC2/Main/Media/ documents/research/ISC2_Cybersecurity_Workforce_Study_2023.pdf?rev=28b46de71ce24e6ab7705f6e3da8637e

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Sliver C2: How Darktrace Provided a Sliver of Hope in the Face of an Emerging C2 Framework

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17
Apr 2024

Offensive Security Tools

As organizations globally seek to for ways to bolster their digital defenses and safeguard their networks against ever-changing cyber threats, security teams are increasingly adopting offensive security tools to simulate cyber-attacks and assess the security posture of their networks. These legitimate tools, however, can sometimes be exploited by real threat actors and used as genuine actor vectors.

What is Sliver C2?

Sliver C2 is a legitimate open-source command-and-control (C2) framework that was released in 2020 by the security organization Bishop Fox. Silver C2 was originally intended for security teams and penetration testers to perform security tests on their digital environments [1] [2] [5]. In recent years, however, the Sliver C2 framework has become a popular alternative to Cobalt Strike and Metasploit for many attackers and Advanced Persistence Threat (APT) groups who adopt this C2 framework for unsolicited and ill-intentioned activities.

The use of Sliver C2 has been observed in conjunction with various strains of Rust-based malware, such as KrustyLoader, to provide backdoors enabling lines of communication between attackers and their malicious C2 severs [6]. It is unsurprising, then, that it has also been leveraged to exploit zero-day vulnerabilities, including critical vulnerabilities in the Ivanti Connect Secure and Policy Secure services.

In early 2024, Darktrace observed the malicious use of Sliver C2 during an investigation into post-exploitation activity on customer networks affected by the Ivanti vulnerabilities. Fortunately for affected customers, Darktrace DETECT™ was able to recognize the suspicious network-based connectivity that emerged alongside Sliver C2 usage and promptly brought it to the attention of customer security teams for remediation.

How does Silver C2 work?

Given its open-source nature, the Sliver C2 framework is extremely easy to access and download and is designed to support multiple operating systems (OS), including MacOS, Windows, and Linux [4].

Sliver C2 generates implants (aptly referred to as ‘slivers’) that operate on a client-server architecture [1]. An implant contains malicious code used to remotely control a targeted device [5]. Once a ‘sliver’ is deployed on a compromised device, a line of communication is established between the target device and the central C2 server. These connections can then be managed over Mutual TLS (mTLS), WireGuard, HTTP(S), or DNS [1] [4]. Sliver C2 has a wide-range of features, which include dynamic code generation, compile-time obfuscation, multiplayer-mode, staged and stageless payloads, procedurally generated C2 over HTTP(S) and DNS canary blue team detection [4].

Why Do Attackers Use Sliver C2?

Amidst the multitude of reasons why malicious actors opt for Sliver C2 over its counterparts, one stands out: its relative obscurity. This lack of widespread recognition means that security teams may overlook the threat, failing to actively search for it within their networks [3] [5].

Although the presence of Sliver C2 activity could be representative of authorized and expected penetration testing behavior, it could also be indicative of a threat actor attempting to communicate with its malicious infrastructure, so it is crucial for organizations and their security teams to identify such activity at the earliest possible stage.

Darktrace’s Coverage of Sliver C2 Activity

Darktrace’s anomaly-based approach to threat detection means that it does not explicitly attempt to attribute or distinguish between specific C2 infrastructures. Despite this, Darktrace was able to connect Sliver C2 usage to phases of an ongoing attack chain related to the exploitation of zero-day vulnerabilities in Ivanti Connect Secure VPN appliances in January 2024.

Around the time that the zero-day Ivanti vulnerabilities were disclosed, Darktrace detected an internal server on one customer network deviating from its expected pattern of activity. The device was observed making regular connections to endpoints associated with Pulse Secure Cloud Licensing, indicating it was an Ivanti server. It was observed connecting to a string of anomalous hostnames, including ‘cmjk3d071amc01fu9e10ae5rt9jaatj6b.oast[.]live’ and ‘cmjft14b13vpn5vf9i90xdu6akt5k3pnx.oast[.]pro’, via HTTP using the user agent ‘curl/7.19.7 (i686-redhat-linux-gnu) libcurl/7.63.0 OpenSSL/1.0.2n zlib/1.2.7’.

Darktrace further identified that the URI requested during these connections was ‘/’ and the top-level domains (TLDs) of the endpoints in question were known Out-of-band Application Security Testing (OAST) server provider domains, namely ‘oast[.]live’ and ‘oast[.]pro’. OAST is a testing method that is used to verify the security posture of an application by testing it for vulnerabilities from outside of the network [7]. This activity triggered the DETECT model ‘Compromise / Possible Tunnelling to Bin Services’, which breaches when a device is observed sending DNS requests for, or connecting to, ‘request bin’ services. Malicious actors often abuse such services to tunnel data via DNS or HTTP requests. In this specific incident, only two connections were observed, and the total volume of data transferred was relatively low (2,302 bytes transferred externally). It is likely that the connections to OAST servers represented malicious actors testing whether target devices were vulnerable to the Ivanti exploits.

The device proceeded to make several SSL connections to the IP address 103.13.28[.]40, using the destination port 53, which is typically reserved for DNS requests. Darktrace recognized that this activity was unusual as the offending device had never previously been observed using port 53 for SSL connections.

Model Breach Event Log displaying the ‘Application Protocol on Uncommon Port’ DETECT model breaching in response to the unusual use of port 53.
Figure 1: Model Breach Event Log displaying the ‘Application Protocol on Uncommon Port’ DETECT model breaching in response to the unusual use of port 53.

Figure 2: Model Breach Event Log displaying details pertaining to the ‘Application Protocol on Uncommon Port’ DETECT model breach, including the 100% rarity of the port usage.
Figure 2: Model Breach Event Log displaying details pertaining to the ‘Application Protocol on Uncommon Port’ DETECT model breach, including the 100% rarity of the port usage.

Further investigation into the suspicious IP address revealed that it had been flagged as malicious by multiple open-source intelligence (OSINT) vendors [8]. In addition, OSINT sources also identified that the JARM fingerprint of the service running on this IP and port (00000000000000000043d43d00043de2a97eabb398317329f027c66e4c1b01) was linked to the Sliver C2 framework and the mTLS protocol it is known to use [4] [5].

An Additional Example of Darktrace’s Detection of Sliver C2

However, it was not just during the January 2024 exploitation of Ivanti services that Darktrace observed cases of Sliver C2 usages across its customer base.  In March 2023, for example, Darktrace detected devices on multiple customer accounts making beaconing connections to malicious endpoints linked to Sliver C2 infrastructure, including 18.234.7[.]23 [10] [11] [12] [13].

Darktrace identified that the observed connections to this endpoint contained the unusual URI ‘/NIS-[REDACTED]’ which contained 125 characters, including numbers, lower and upper case letters, and special characters like “_”, “/”, and “-“, as well as various other URIs which suggested attempted data exfiltration:

‘/upload/api.html?c=[REDACTED] &fp=[REDACTED]’

  • ‘/samples.html?mx=[REDACTED] &s=[REDACTED]’
  • ‘/actions/samples.html?l=[REDACTED] &tc=[REDACTED]’
  • ‘/api.html?gf=[REDACTED] &x=[REDACTED]’
  • ‘/samples.html?c=[REDACTED] &zo=[REDACTED]’

This anomalous external connectivity was carried out through multiple destination ports, including the key ports 443 and 8888.

Darktrace additionally observed devices on affected customer networks performing TLS beaconing to the IP address 44.202.135[.]229 with the JA3 hash 19e29534fd49dd27d09234e639c4057e. According to OSINT sources, this JA3 hash is associated with the Golang TLS cipher suites in which the Sliver framework is developed [14].

結論

Despite its relative novelty in the threat landscape and its lesser-known status compared to other C2 frameworks, Darktrace has demonstrated its ability effectively detect malicious use of Sliver C2 across numerous customer environments. This included instances where attackers exploited vulnerabilities in the Ivanti Connect Secure and Policy Secure services.

While human security teams may lack awareness of this framework, and traditional rules and signatured-based security tools might not be fully equipped and updated to detect Sliver C2 activity, Darktrace’s Self Learning AI understands its customer networks, users, and devices. As such, Darktrace is adept at identifying subtle deviations in device behavior that could indicate network compromise, including connections to new or unusual external locations, regardless of whether attackers use established or novel C2 frameworks, providing organizations with a sliver of hope in an ever-evolving threat landscape.

Credit to Natalia Sánchez Rocafort, Cyber Security Analyst, Paul Jennings, Principal Analyst Consultant

付録

DETECT Model Coverage

  • Compromise / Repeating Connections Over 4 Days
  • Anomalous Connection / Application Protocol on Uncommon Port
  • Anomalous Server Activity / Server Activity on New Non-Standard Port
  • Compromise / Sustained TCP Beaconing Activity To Rare Endpoint
  • Compromise / Quick and Regular Windows HTTP Beaconing
  • Compromise / High Volume of Connections with Beacon Score
  • Anomalous Connection / Multiple Failed Connections to Rare Endpoint
  • Compromise / Slow Beaconing Activity To External Rare
  • Compromise / HTTP Beaconing to Rare Destination
  • Compromise / Sustained SSL or HTTP Increase
  • Compromise / Large Number of Suspicious Failed Connections
  • Compromise / SSL or HTTP Beacon
  • Compromise / Possible Malware HTTP Comms
  • Compromise / Possible Tunnelling to Bin Services
  • Anomalous Connection / Low and Slow Exfiltration to IP
  • Device / New User Agent
  • Anomalous Connection / New User Agent to IP Without Hostname
  • Anomalous File / EXE from Rare External Location
  • Anomalous File / Numeric File Download
  • Anomalous Connection / Powershell to Rare External
  • Anomalous Server Activity / New Internet Facing System

侵害指標(IoC)一覧

18.234.7[.]23 - Destination IP - Likely C2 Server

103.13.28[.]40 - Destination IP - Likely C2 Server

44.202.135[.]229 - Destination IP - Likely C2 Server

参考文献

[1] https://bishopfox.com/tools/sliver

[2] https://vk9-sec.com/how-to-set-up-use-c2-sliver/

[3] https://www.scmagazine.com/brief/sliver-c2-framework-gaining-traction-among-threat-actors

[4] https://github[.]com/BishopFox/sliver

[5] https://www.cybereason.com/blog/sliver-c2-leveraged-by-many-threat-actors

[6] https://securityaffairs.com/158393/malware/ivanti-connect-secure-vpn-deliver-krustyloader.html

[7] https://www.xenonstack.com/insights/out-of-band-application-security-testing

[8] https://www.virustotal.com/gui/ip-address/103.13.28.40/detection

[9] https://threatfox.abuse.ch/browse.php?search=ioc%3A107.174.78.227

[10] https://threatfox.abuse.ch/ioc/1074576/

[11] https://threatfox.abuse.ch/ioc/1093887/

[12] https://threatfox.abuse.ch/ioc/846889/

[13] https://threatfox.abuse.ch/ioc/1093889/

[14] https://github.com/projectdiscovery/nuclei/issues/3330

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著者について
Natalia Sánchez Rocafort
Cyber Security Analyst
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