Blog

Inside the SOC

Darktraceがフィッシング攻撃につながる大規模なアカウントハイジャックを検知した実例

Default blog imageDefault blog imageDefault blog imageDefault blog imageDefault blog imageDefault blog image
19
May 2023
19
May 2023
このブログでは、Darktraceが大規模なSaaSの侵害を検知し、その後、教育機関を経由して伝播したフィッシング攻撃について説明します。

はじめに 

SaaSプラットフォームや多要素認証(MFA)サービスの普及を利用して、悪意あるアクターが組織のネットワークに不正にアクセスすることが後を絶たない中、アカウントの侵害を早い段階で防ぐために適切なセキュリティツールを導入することが極めて重要となっています。

攻撃者が頻繁に使用する手法の1つに、アカウントの乗っ取りがあります。アカウントの乗っ取りは、脅威アクターが認証情報を悪用してSaaSアカウントにログインする際に発生します。多くの場合、本物の攻撃者は通常ログインしないような珍しい場所からログインします。 

これらのアカウントへのアクセスは、フィッシングメールやパスワードスプレー攻撃によって認証情報を採取したり、ユーザーアカウントでMFAを有効にせず、認証にユーザー認証情報のみを必要とするなど、安全でないクラウド防御対策を悪用することで引き起こされます。アカウントの完全性が侵害されると、脅威アクターはマルウェアの配信、機密データの読み取りと流出、さらに社内外のユーザー認証情報を採取するためのフィッシングメールの送信など、さらなる活動を行い、攻撃サイクルを繰り返すことができます [1,2]。 

2023年初頭、 Darktraceは、教育分野の顧客のネットワーク上で大規模なアカウント乗っ取りとフィッシング攻撃を検知し、数百のアカウントに影響を与え、数千のEメールがネットワーク外に転送される結果となりました。Darktrace  DETECT™が提供する極めて高い可視性により、キルチェーンのあらゆる段階で敵対的な活動を検知することができました。Ask the Expert(ATE)サービスを通じてDarktrace Analystチームから直接サポートを受けることにより、顧客は十分に情報を得て改善策を実施できるようになりました。 

一連の攻撃の詳細

Darktrace はその結果、お客様のネットワーク上で乗っ取られた全てのアカウントで、見知らぬ場所からのログイン、すべての受信メールを悪意のあるEメールアドレスに転送するというメール転送ルールの有効化、フィッシングメールの送信とその削除という同じパターンの活動を確認しました。 

図1:乗っ取られたSaaSアカウントへの攻撃のタイムライン

初期アクセス

Darktrace DETECTは、2023年1月14日に顧客環境上の異常なSaaSアクティビティを最初に検知し、その後2月3日にも、複数のSaaSアカウントが、珍しいIPアドレスと地理的に不可能な移動タイミングを持つ非定型の場所からログインしていること、またはアカウント所有者が他の場所で活動している間にログインしていることが観察されました。オープンソースインテリジェンス(OSINT)ソースを使用したその後の調査で、IPアドレスの1つが最近ブルートフォースまたはパスワードスプレーの試みに関連していたことが判明しました。

このような異常なログインのパターンは、攻撃の期間中ずっと続き、毎日、より多くのユニークなアカウントが同様の異常なログインでモデルブリーチを発生させました。これらのユーザーのログインにはMFA認証が適用されなかったため、認証に認証情報のみを必要とすることで、最初の侵入プロセスが可能になりました。

Eメールを送信する 

また、侵害されたアカウントは、「Email HELP DESK」という件名のメールを外部および内部の受信者に送信していることが確認されました。これは、脅威者が社内のヘルプデスクを装って受信者の信頼を得るためにソーシャルエンジニアリング戦術を採用したものと思われます。

Eメールを転送する

ログインに成功した後、侵害されたアカウントは、外部のEメールアドレスにEメールを転送するためのEメールルールを作成し始め、そのうちのいくつかは、OSINTソースによると悪意のある活動のためのドメインに関連していたことが判明しました [3]。

  • chotunai[.]com
  • bymercy[.]com
  • breazeim[.]com
  • brandoza[.]com

Eメールの転送は、SaaSの侵害行為において、通信回線を制御するためによく見られる手口です。悪意のある脅威アクターは、機密情報の流出、侵害されたEメールへの持続的なアクセスの獲得、請求書支払いのリダイレクトなど、不正な目的のために進行中の通信に介入しようとすることがよくあります。 

Eメールを削除する

Eメール転送の直後、感染したアカウントが一斉に異常なEメールを削除したことが検知されました。さらに調査を進めると、これらのアカウントは以前に大量のフィッシングメールを送信しており、この大量削除は、送信トレイから削除することでこれらの活動を隠そうとしたものと思われます。

2月10日、この顧客はDarktrace が侵害されたと特定したすべてのアカウントにパスワードの一括リセットを適用し、MFAを備えた特権アカウントのプロビジョニングを行いました。これらの対策により、最初の侵入経路に対処し、侵害を食い止めることに成功したと発表しています。  

Darktrace のカバレッジ

Darktrace は、自己学習型AIを駆使して、アカウントが悪意のあるアクターに乗っ取られたことを示す可能性のある異常なSaaSアクティビティを検知する能力を効果的に実証しました。従来のルールやシグネチャベースのアプローチに頼るのではなく、Darktrace のモデルはネットワーク自体の理解を深め、危険なものが予想される生活パターンから逸脱した場合に瞬時に認識することができます。

図2:乗っ取られたSaaSアカウントでの異常なSaaSアクティビティの検知

初期アクセス

初期アクセスは以下のモデルで検知されました:

  • Security Integration / High Severity Integration Detection  
  • SaaS / Unusual Activity / Activity from Multiple Unusual IPs 
  • SaaS / Access / Unusual External Source for SaaS Credential Use 
  • SaaS / Compromise / Login From Rare Endpoint While User Is Active 

初期アクセスは、以下のCyber AI Analyst インシデントでも検知されました:

  • Possible Hijack of Office365 Account 

モデルブリーチとAI Analystのインシデントでは、図3に描かれているように、MFAの使用不足と合わせて、100%レアな外部IPアドレスからのログインが検知されました。

Figure 3: Breach log showing initial detection of a SaaS login from a 100% rare IP where MFA was not used.
図4:Darktrace のSaaSコンソールで可視化された異常なSaaSアクティビティの初期検知

Eメールを転送する

Eメール転送は、以下のモデルで検知されました:

  • SaaS / Admin / Mail Forwarding Enabled 

攻撃されたアカウントの多くは、外部Eメールアドレスへのメール転送ルールを設定しており、表向きは、ネットワーク上での永続性を確立し、機密性が高い通信を流出させるために検知されました。

図5:Eメール転送の有効化は、当該アカウントで100%新規または珍しいものとして検知された

大量のEメール削除

大量のEメール削除は、以下のモデルで検知されました:

  • SaaS / Compromise / Suspicious Login and Mass Email Deletes 
  • SaaS / Resource / Mass Email Deletes from Rare Location 
図6: 危殆化したアカウントが、以前に送信したフィッシングメールを送信トレイから削除

Darktraceは、稀な場所から非常に異常な大量メール削除を行うアカウントを検知しました。この攻撃者は、「Email HELP DESK」というメールを削除しており、後にこの攻撃で使用された主要なフィッシングメールであることが確認されました。削除は侵害されたアカウントの送信トレイで観察され、おそらく悪意のある活動を隠すために行われたものと思われます。

Darktraceは、この連動した活動のパターンを、以下のようなシーケンシャルなモデルでも検知しました: 

  • SaaS / Compromise / Unusual Login, Sent Mail, Deleted Sent
  • SaaS / Compromise / Suspicious Login and Mass Email Deletes 

Ask the Expert

お客様は、ATE(Ask The Expert)サービスを利用して、攻撃に関するより多くの技術的な情報とサポートを要求しました。Darktraceの24時間365日体制のアナリストチームは、専門的な支援とさらなる詳細を提供し、その後の調査や修復のステップを支援することができました。 

さらなる検知と遮断  

残念ながら、このお客様は攻撃時にDarktrace/Email™を有効にしていませんでした。Darktrace/Emailは、インバウンドおよびアウトバウンドのメールフローを可視化することで、潜在的なデータ損失インシデントを監視することができます。この場合、Darktrace DETECT/Emailは、侵害されたアカウントから送信されたフィッシングメールや、攻撃者が社内のヘルプデスクになりすまそうとした試みを完全に可視化することができたと思われます。さらに、新たにAnalysis Outlookとの統合により、従業員はメールが疑わしい理由を理解し、セキュリティチームに直接メールを報告できるようになり、フィッシング攻撃に対するユーザーの意識を継続的に高めることができます。 

Darktrace/Emailは、Darktrace/Network™の検知を強化します。Darktrace/Network内の「Email Nexus」モデルをトリガーとして、デジタル資産全体で悪意のある活動を検知し、SaaSの不正ログインから不正ユーザーによって送信された大量のスパムメールまでを関連付けます。 

図7:Darktrace/Emailによって強化されたDarktrace/Network内のEmail Nexusモデル

Darktrace RESPOND™ は攻撃時に顧客環境で有効になっていませんでした。もし有効になっていれば、Darktraceはキルチェーンの複数にわたって検知されたSaaSモデルの侵害に対して自律的に行動を起こすことができたはずです。RESPONDは、乗っ取られたアカウントを無効にするか、一定期間強制的にログアウトさせ、悪意のある行為者によって確立された受信トレイのルールも無効にすることができたでしょう。これにより、顧客のセキュリティチームは、インシデントを分析し、状況を緩和するための貴重な時間を得ることができ、攻撃がこれ以上拡大することを防ぐことができました。 

結論

最終的に、Darktraceは、この大規模な標的型SaaSアカウントの乗っ取りとその後のフィッシング攻撃を検知することができた顧客ネットワーク上の比類のない可視性を示しました。これは、深層防御の重要性を強調するもので、決定的に重要なのは、この環境ではMFAが実施されていなかったため、標的となった組織がクレデンシャルの盗難による危険にさらされる可能性が高かったことです。また、このアカウント侵害の後にDarktraceが検知したフィッシング活動は、あらゆるセキュリティスタックにおけるEメール保護の必要性を強調しています。 

Darktraceの可視性により、アカウントのログイン、メール転送ルールの作成、送信メール、フィッシングメールの大量削除など、高度な粒度で攻撃を自律検知することができました。Darktraceの異常検知は、新たな脅威を特定する際に、シグネチャやルール、既知の侵害指標(IoC)に頼る必要がなく、代わりにユーザーの通常の行動からの逸脱を認識することに重点を置いていることを意味します。

しかし、進行中の攻撃に即座に介入して停止させることができる自律的な遮断技術が存在しなければ、組織は常に被害が発生した後に攻撃に対処することになります。Darktrace RESPONDは、疑わしい活動を検知するとすぐに対策を講じ、攻撃が拡大するのを防ぎ、お客様のビジネスに大きな支障をきたさないようにするためのユニークな存在です。

Credit to: Zoe Tilsiter, Cyber Analyst, Gernice Lee, Cyber Analyst.

付録

モデルブリーチ

SaaS / Access / Unusual External Source for SaaS Credential Use

SaaS / Admin / Mail Forwarding Enabled

SaaS / Compliance / Microsoft Cloud App Security Alert Detected

SaaS / Compromise / SaaS Anomaly Following Anomalous Login 

SaaS / Compromise / Unusual Login, Sent Mail, Deleted Sent

SaaS / Compromise / Suspicious Login and Mass Email Deletes 

SaaS / Resource / Mass Email Deletes from Rare Location

SaaS / Unusual Activity / Multiple Unusual External Sources For SaaS Credential

SaaS / Unusual Activity / Activity from Multiple Unusual IPs

SaaS / Unusual Activity / Multiple Unusual SaaS Activities 

Security Integration / Low Severity Integration Detection

Security Integration / High Severity Integration Detection

IoC一覧

brandoza[.]com - domain - probable domain of forwarded email address

breazeim[.]com - domain - probable domain of forwarded email address

bymercy[.]com - domain - probable domain of forwarded email address

chotunai[.]com - domain - probable domain of forwarded email address

MITRE ATT&CK マッピング

Tactic: INITIAL ACCESS, PERSISTENCE, PRIVILEGE ESCILATION, DEFENSE EVASION

Technique: T1078.004 – Cloud Accounts

Tactic: COLLECTION

Technique: T1114- Email Collection

Tactic:COLLECTION

Technique: T1114.003- Email Forwarding Rule

Tactic: IMPACT

Technique: T1485 - Data Destruction

Tactic: DEFENSE EVASION

Technique: T1578.003 – Delete Cloud Instance

参考文献

[1] Darktrace, 2022, Cloud Application Security_ Protect your SaaS with Self-Learning AI.pdf

[2] https://www.cloudflare.com/en-gb/learning/access-management/account-takeover/ 

[3] https://www.virustotal.com/gui/domain/chotunai.com 

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.
AUTHOR
ABOUT ThE AUTHOR
Zoe Tilsiter
Cyber Analyst
Book a 1-1 meeting with one of our experts
この記事を共有

More in this series

該当する項目はありません。

Blog

該当する項目はありません。

The State of AI in Cybersecurity: How AI will impact the cyber threat landscape in 2024

Default blog imageDefault blog image
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

続きを読む
著者について

Blog

Inside the SOC

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

Default blog imageDefault blog image
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

続きを読む
著者について
Natalia Sánchez Rocafort
Cyber Security Analyst
Our ai. Your data.

Elevate your cyber defenses with Darktrace AI

無償トライアルを開始
Darktrace AI protecting a business from cyber threats.