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Common Attack Vectors and Mitigation Strategies for Google Workspace

This guide documents prevalent attack vectors targeting Google Workspace environments and provides actionable mitigation strategies for each. It is designed for security professionals and MSPs protecting client environments.

1. Account Compromise Attacks

Attack Techniques

Attack Vector	Description	Indicators
Credential Stuffing	Automated attempts to use breached passwords across multiple services	Multiple failed logins followed by successful login, authentication from unusual locations
Phishing	Sophisticated emails impersonating Google or trusted parties to steal credentials	User reports of suspicious emails, unexpected password reset emails, login from new locations
Password Spraying	Low-volume attempts using common passwords against multiple accounts	Failed login attempts across multiple user accounts with similar patterns
Man-in-the-Middle	Intercepting traffic between users and Google services	Unexpected certificate warnings, login from unusual network paths
Session Hijacking	Stealing authentication cookies to impersonate authenticated users	Multiple concurrent sessions, unusual application access patterns

Mitigation Strategies

1. Technical Controls
2. Implement Multi-Factor Authentication (MFA) for all users
3. Deploy security keys for high-value accounts
4. Enable enhanced safe browsing features in Chrome
5. Implement DMARC, SPF, and DKIM email authentication

6. Configure account recovery options securely

7. Detection Capabilities

8. Monitor for authentication from unusual locations, devices, or times
9. Create alerts for MFA enrollment changes or disablement
10. Track concurrent sessions across geographically distant locations
11. Monitor for unusual numbers of failed login attempts

12. Implement impossible travel detection

13. User Education

14. Train users to identify phishing attempts
15. Implement phishing simulation exercises
16. Create clear incident reporting procedures
17. Educate on secure password practices
18. Promote awareness of social engineering techniques

2. OAuth and Third-Party Application Abuse

Attack Techniques

Attack Vector	Description	Indicators
Malicious Applications	Convincing users to authorize malicious apps with excessive permissions	Unusual OAuth grants, unfamiliar applications with sensitive scopes
OAuth Phishing	Targeted phishing specifically designed to trick users into granting OAuth tokens	Applications requesting unusual combinations of scopes, OAuth grants to new domains
Token Theft	Stealing and exploiting OAuth refresh tokens	Unexpected application access, authentication from unusual locations using valid tokens
Excessive Permissions	Legitimate apps requesting more permissions than necessary	Applications with read/write scopes when read-only would suffice
Shadow IT Applications	Unauthorized applications connected to Google Workspace	Unknown applications accessing company data, inconsistent authorization patterns

Mitigation Strategies

1. Technical Controls
2. Implement OAuth application allowlisting
3. Restrict third-party access to sensitive Google API scopes
4. Enforce app verification for sensitive scopes
5. Regularly audit and prune authorized applications

6. Implement data access monitoring for third-party apps

7. Detection Capabilities

8. Monitor for new OAuth application authorizations
9. Create alerts for sensitive scope authorizations
10. Track application usage patterns for anomalies
11. Monitor for applications used by only one or few users

12. Implement unusual application behavior detection

13. Governance Controls

14. Develop and enforce an application approval process
15. Create an acceptable third-party application policy
16. Maintain an inventory of approved applications
17. Conduct regular security reviews of connected applications
18. Implement a formal application decommissioning process

3. Data Exfiltration Attacks

Attack Techniques

Attack Vector	Description	Indicators
Excessive Downloads	Downloading unusually large amounts of data from Google services	Abnormal volume of Drive downloads, export of entire mailboxes
Unusual Sharing	Sharing sensitive content externally or with personal accounts	Sudden increase in external sharing, sharing sensitive folders
Email Forwarding	Setting up forwarding rules to external addresses	Creation of new mail forwarding rules, especially to personal domains
Drive Synchronization	Synchronizing company data to unmanaged personal devices	New Drive sync clients, sync to unusual devices
Takeout Service Abuse	Using Google Takeout to extract complete data archives	Unexpected Takeout requests, especially from unusual locations

Mitigation Strategies

1. Technical Controls
2. Implement Data Loss Prevention (DLP) policies
3. Restrict external sharing based on content classification
4. Control email forwarding to external domains
5. Set Drive synchronization policies for approved devices

6. Restrict Google Takeout access where appropriate

7. Detection Capabilities

8. Monitor for unusual download volumes or patterns
9. Create alerts for first-time external sharing of sensitive data
10. Track new email forwarding rules
11. Monitor for new device synchronization

12. Implement abnormal data access detection

13. Data Governance

14. Implement data classification and handling policies
15. Conduct regular data access reviews
16. Create clear data sharing guidelines
17. Establish appropriate data retention policies
18. Implement controls aligned with data sensitivity

4. Email-Based Attacks

Attack Techniques

Attack Vector	Description	Indicators
Business Email Compromise	Targeted impersonation of executives for fraud	Unexpected financial requests, slightly altered sender domains
Malware Attachments	Malicious payloads delivered via email attachments	Unusual file types, attachments with macros, executable content
Embedded Links	Emails with links to credential phishing or malware sites	URLs with typosquatted domains, shortened links, credential submission forms
Conversation Hijacking	Inserting into existing email threads with malicious content	Sudden topic changes in email threads, unexpected attachments in ongoing conversations
Email Spoofing	Sending emails that appear to come from trusted domains	Authentication failures, sender inconsistencies, unusual reply-to addresses

Mitigation Strategies

1. Technical Controls
2. Implement advanced phishing and malware protection
3. Enable enhanced pre-delivery message scanning
4. Configure strict SPF, DKIM, and DMARC policies
5. Implement attachment scanning and sandboxing

6. Deploy link protection and URL rewriting

7. Detection Capabilities

8. Monitor for emails failing authentication checks
9. Create alerts for potential business email compromise patterns
10. Track unusual sending patterns or volumes
11. Implement suspicious attachment detection

12. Monitor for unusual recipient patterns

13. Process Controls

14. Establish out-of-band verification for sensitive requests
15. Create clear procedures for financial authorization
16. Implement policies for handling suspicious emails
17. Conduct regular phishing simulation exercises
18. Establish email security incident response procedures

5. Privilege Escalation Attacks

Attack Techniques

Attack Vector	Description	Indicators
Admin Account Targeting	Focused attacks on administrative users	Targeted phishing against admins, unusual admin console access
Role Privilege Abuse	Exploiting excessive privileges assigned to roles	Unexpected administrative actions, privilege use outside job function
Delegated Admin Exploitation	Abusing partner or delegated admin access	Administrative actions from partners outside maintenance windows
Developer API Abuse	Exploiting API access to elevate privileges	Unusual API calls, unexpected permission changes via API
Recovery Options Manipulation	Changing account recovery information to gain access	Modifications to recovery email addresses or phone numbers

Mitigation Strategies

1. Technical Controls
2. Implement strict privileged access management
3. Enforce separation of administrative accounts
4. Apply enhanced security for admin accounts
5. Restrict administrative API access

6. Implement time-bound admin access

7. Detection Capabilities

8. Monitor all administrative actions
9. Create alerts for unusual administrative behavior
10. Track role and privilege changes
11. Implement privileged account usage monitoring

12. Alert on recovery option changes for sensitive accounts

13. Administrative Policies

14. Implement and enforce least privilege principles
15. Conduct regular privilege access reviews
16. Create clear administrative access request procedures
17. Establish emergency access protocols
18. Document privileged account inventory

6. Lateral Movement Techniques

Attack Techniques

Attack Vector	Description	Indicators
Service Account Pivoting	Using compromised service accounts to move between systems	Service account usage from unusual sources, credential reuse
OAuth Token Abuse	Using stolen tokens to access multiple interconnected services	Access to multiple services in rapid succession, unusual service combinations
Shared Document Exploitation	Using document sharing to deliver malicious content	Unusual internal sharing patterns, documents with suspicious macros or links
Cross-Application Movement	Leveraging access to one Google service to compromise others	Unexpected cross-service access patterns, rapid pivoting between services
Workspace Add-on Abuse	Exploiting authorized add-ons to gain additional access	Add-on behavior changes, unusual data access by add-ons

Mitigation Strategies

1. Technical Controls
2. Implement service boundaries and segmentation
3. Control service account permissions strictly
4. Limit sharing capabilities based on data classification
5. Configure add-on restrictions and approvals

6. Implement context-aware access controls

7. Detection Capabilities

8. Monitor for unusual cross-service access patterns
9. Create alerts for anomalous service account usage
10. Track document access and sharing patterns
11. Implement service-to-service connection monitoring

12. Monitor for unusual add-on behavior

13. Security Architecture

14. Design service boundaries with security in mind
15. Segment data and services by sensitivity
16. Implement zero trust principles for service access
17. Create clear data flow diagrams and controls
18. Establish service-to-service authentication requirements

7. Persistence Mechanisms

Attack Techniques

Attack Vector	Description	Indicators
Secondary Account Creation	Creating additional accounts for persistent access	New account creation outside standard processes, accounts with similar names to existing users
App Script Backdoors	Implementing malicious Google Apps Scripts	Unexpected script creation or modification, scripts with unusual permissions or triggers
Rogue App Deployment	Deploying unauthorized applications with persistent access	New application deployments outside change control, applications with unusual permissions
Mail Rules and Filters	Establishing email rules to hide detection communications	Creation of unusual mail filtering rules, rules that hide specific senders or subjects
OAuth Persistence	Maintaining persistent access via authorized applications	Applications with long-lived tokens, unusual refresh token usage

Mitigation Strategies

1. Technical Controls
2. Implement strict user provisioning controls
3. Control Apps Script creation and permissions
4. Restrict application deployment capabilities
5. Monitor and control email rule creation

6. Implement token lifetime limitations

7. Detection Capabilities

8. Monitor for unauthorized account creation
9. Create alerts for suspicious script activities
10. Track application deployment outside normal processes
11. Implement mail rule change monitoring

12. Monitor for unusual OAuth token persistence

13. Operational Security

14. Conduct regular account reviews and reconciliation
15. Implement formal application deployment processes
16. Create clear deprovisioning procedures
17. Establish script development and review guidelines
18. Conduct regular environment security scanning

MSP-Specific Attack Surface Considerations

For MSPs managing multiple Google Workspace tenants, additional attack vectors include:

Partner Account Compromise

• Attack: Targeting MSP staff accounts with partner/reseller privileges
• Impact: Potential access to multiple client environments
• Mitigation:
• Implement enhanced MFA for all partner accounts
• Restrict partner admin capabilities to least required privilege
• Create partner-level activity monitoring and alerting
• Establish strict partner access request and approval processes
• Conduct regular partner privilege reviews

Cross-Tenant Attack Propagation

• Attack: Using compromised access in one tenant to pivot to others
• Impact: Multiple client compromise from single initial access
• Mitigation:
• Implement strong tenant isolation practices
• Create separate administrative accounts per tenant
• Avoid credential reuse across client environments
• Establish cross-tenant security monitoring
• Implement tenant-specific security baselines

Incident Response Considerations

When responding to Google Workspace security incidents:

1. Initial Assessment
2. Identify affected accounts and services
3. Determine authentication indicators (IP, device, location)
4. Assess timeline of suspicious activities
5. Evaluate data access and potential exfiltration

6. Identify potential persistence mechanisms

7. Containment Steps

8. Force account sign-out for affected users
9. Implement temporary access restrictions
10. Reset passwords for affected accounts
11. Revoke suspicious OAuth tokens

12. Block suspicious IP addresses

13. Recovery Actions

14. Restore from backups if necessary
15. Remediate any discovered persistence mechanisms
16. Re-establish proper permissions and access controls
17. Conduct post-recovery security assessment
18. Implement additional preventative controls

Threat Intelligence Resources

• Google Workspace Security Alerts
• Google Safe Browsing
• CISA Threat Advisories
• MITRE ATT&CK Cloud Techniques
• Cloud Security Alliance Threat List

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Note: This guide should be regularly updated to reflect emerging attack techniques and mitigation strategies.