The Silent Siphon¶

The Fungolia Ministry of Digital Affairs (FMDA) investigates this breach and tracks all steps the adversaries have taken for a better understanding and which defensive measures can be taken.

• Designation: APT-41 (“Crimson Weave”)

• Target: Fungolian Government Ministry of Foreign Affairs (FMFA)

• TTPs: Credential Stuffing, OAuth App Abuse, Mailbox Rule Manipulation

• Objective: Establish persistent, silent access to exfiltrate diplomatic correspondence and intelligence.

Phase 1: Initial Access - The Keys Under the Mat¶

Goal: Gain a foothold within the target’s Microsoft 365 environment by exploiting password reuse.

Narrative: Your first step is not to break down the door but to find a key that was carelessly copied and left under the mat. You begin by aggregating data from past, unrelated breaches of platforms like LinkedIn, Adobe, or former government contractors. Using automated tools, you comb through these millions of credentials specifically for email addresses belonging to the @gov-minfa.[country] domain.

The Attack Chain:

1. Acquire the Credential Set: A purchased database from a breached third-party vendor contains the email j.doe@gov-minfa.[country] and the password Spring2023!.

2. Test for Reuse: You automate a login attempt against the target’s Outlook Web Access (OWA) portal (outlook.office.com). The attempt is successful. The user has not enabled multi-factor authentication (MFA), and the password has not been changed since the third-party breach.

3. Access Granted: You now have a valid session cookie and full access to Johannes Doe’s mailbox.

Why It Works:

• Human Factor: Password reuse across personal and professional accounts is rampant.

• Technical Control Gap: Lack of enforced MFA and inadequate credential rotation policies.

Phase 2: Establish Foothold - The Invisible Tenant¶

Goal: Create multiple, persistent access methods that are difficult to detect and will survive a password reset.

Narrative: You’re inside the apartment, but you need to make copies of the key and set up a way to see everything that comes through the mail slot, even if the locks are changed.

The Attack Chain:

1. Inbox Rule Persistence:

   • Action: Within the OWA settings, you create a new mail rule named “_MSGTAG” (designed to blend in with system-generated rules).

   • Function: The rule is configured to silently forward a copy of every incoming and outgoing email to an attacker-controlled external email address (mbx.analytics@protonmail.com).

   • Stealth: The rule is set to not notify the user of its action.

2. OAuth Application Persistence:

   • Action: You navigate to Azure Active Directory within the M365 portal and register a new “Multi-Tenant” application. It is given a benign name like “Microsoft Telemetry Service” and requests permissions to Mail.Read, Mail.ReadWrite, and User.Read.All.

   • Function: This grants your external command-and-control (C2) server long-lived API tokens to access the mailbox programmatically. Crucially, these tokens are independent of the user’s password and will remain valid even if Johannes Doe changes his password tomorrow.

   • Stealth: The application registration is visible in the Azure AD admin portal, but it easily blends in with dozens of other legitimate third-party integrations and is unlikely to be audited by non-specialist staff.

Why it works:

• Trust Exploitation: Users and admins are conditioned to trust integrations within their M365 environment.

• Visibility Gap: Mailbox forwarding rules and OAuth app consent are not actively monitored by most organisations’ SOCs.

Phase 3: Privilege Escalation & Lateral Movement - Blending into the Hallways¶

Goal: Expand access from a single mailbox to more valuable sources of intelligence within the organisation.

Narrative: From Johannes’s small apartment, you now have access to the building’s directory. You can identify and enter the larger, more important offices down the hall.

The Attack Chain:

1. Enumeration: Using the granted OAuth tokens, your C2 server makes Microsoft Graph API calls to:

   • List all available users (GET /users).

   • List all available shared mailboxes and distribution groups (GET /groups).

2. Target Identification: The scan reveals high-value targets:

   • eudelegation.shared@... - A shared mailbox for EU negotiation briefings.

   • legal.council.shared@... - A mailbox for legal counsel on international agreements.

3. Access: Your application’s permissions, granted by the initial compromised account, allow you to read and export mail from these shared resources. No further exploitation is needed.

Why It Works:

• Permission Model Flaw: Overly permissive default settings on shared mailboxes allow any organisation member to access them.

Phase 4: Persistence & Command & Control - The Silent Observer¶

Goal: Maintain long-term, undetected access for data exfiltration.

Narrative: Your presence is now entirely abstract. You are not a person in the building; you are a ghost that reads the mail and listens to the meetings.

The Attack Chain:

• C2 Channels: All communication is performed over legitimate HTTPS traffic to Microsoft’s graph.microsoft.com API endpoints. This traffic is indistinguishable from normal Office 365 activity to most network monitoring tools.

• Data Exfiltration: Data is siphoned out slowly and at random intervals, disguised as normal user traffic, to avoid triggering data loss prevention (DLP) thresholds.

• Calendar Surveillance: The API is also used to read the target’s calendar (GET /me/events), providing a perfect timeline of ministerial movements, meetings, and diplomatic engagements.

Why It Works:

• Trusted Platform: Attackers “hide in plain sight” by using the victim’s own, trusted cloud provider for C2.

• No Malware: There is no malicious file to scan for, no anomalous process to detect. The “malware” is essentially a configuration file (the OAuth token) on a server you control.

Phase 5: Action on Objectives - The Harvest¶

Goal: Fulfill the mission of collecting sensitive diplomatic intelligence.

The Result:

• Full-Scale Intelligence Gathering: For weeks or months, the APT group silently exfiltrates:

  • Draft negotiation positions for upcoming EU-China trade talks.

  • Diplomatic cables concerning strategic partnerships.

  • Internal legal analyses of sanctions packages.

  • The complete calendar and contact network of the Foreign Minister.

• Total Compromise: The government’s sensitive diplomatic communications are fully exposed to a hostile actor, with no indication that a breach has occurred. The compromise is only discovered months later during an unrelated audit or because of a tip-off from an allied intelligence agency.

Summary of attacker advantages & defensive mitigations¶