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SharePoint Online is widely used inside Microsoft 365 and often becomes a focal point for attackers looking to move laterally, stage data, or persist. The following Q&A walks through common adversary steps, practical examples, and defender actions IT teams can take.
SharePoint is attractive because it centralizes sensitive files, integrates across Microsoft 365, and exposes rich APIs that support automation. Attackers can find user content, metadata, and configuration via Graph APIs and search features, which speeds reconnaissance. Because SharePoint links are often trusted inside an organization, malicious content hosted there can bypass domain reputation checks. It also stores permissions and sharing settings that, if abused, enable wide data exposure. Finally, integration with Teams, OneDrive, and Power Platform creates multiple paths for lateral movement and persistence.
Attackers typically begin mapping by listing site collections, libraries, and common URLs to build a site map quickly. They use automated scripts or Graph Search queries to enumerate sites, drive items, and shared links. Publicly indexed documents and naming conventions give clues about sensitive locations like HR or finance sites. Metadata fields and site titles can reveal organizational structure helpful for targeted theft. The goal is to identify high-value content stores and weakly protected sharing links.
Attackers upload macro-enabled or otherwise weaponized Office files to SharePoint, then generate sharing links that look like native business documents. Recipients see a familiar domain and are more likely to trust and open the file, increasing the success rate of social engineering. Once executed, embedded macros or scripts can fetch remote payloads or collect credentials. Because the file is hosted on Microsoft infrastructure, email-based filters and URL reputation checks are often less effective. Using descriptive titles like "HR Update" or "Benefits Summary" improves credibility.
Stolen access or refresh tokens let attackers act as legitimate users without re-entering credentials or triggering MFA. Tokens can be harvested from browser caches, app storage, or device backups, then replayed against Graph endpoints. With a valid token, an attacker can enumerate drives, read files, and create sharing links. If refresh tokens are obtained, long-term access is possible and attackers can mint new access tokens. This method bypasses many traditional detection signals because actions appear to come from the compromised identity.
Attackers search for or brute-force anonymous "anyone with the link" links and then access content without authentication. These links are often created for convenience and forgotten, leaving sensitive data exposed. Automated tools and search engine dorking can enumerate such URLs or index public documents. Once located, an attacker can download files, extract credentials, and identify paths for further exploitation. Regularly auditing external sharing reduces this exposure significantly.
Attackers can create or compromise guest accounts via B2B invitation APIs and then use those identities to access sites and files. If invitation flows or guest permissions aren't tightly controlled, these accounts can be granted broad access. Threat actors may blend in as legitimate external collaborators, making detection harder. Monitoring invitation patterns and limiting guest permissions to least privilege helps mitigate this vector. Removing stale guests and enforcing conditional access policies reduces the risk.
Graph exposes search and drive endpoints that, with even limited delegated permissions, let attackers locate files, sites, and shared links at scale. Queries like /search/query or drive root listings can reveal content across the tenant. Attackers automate these calls to index file names, metadata, and permissions quickly. Rate limits and logging are often insufficient to stop stealthy enumeration. Restricting app permissions and monitoring unusual Graph usage patterns are critical defenses.
Persistence often involves creating backdoor accounts, adding malicious files with embedded links, or modifying flows and site scripts to exfiltrate data over time. Attackers may plant scheduled tasks via automated flows, or use OAuth clients with excessive permissions to maintain long-lived access. Lateral movement happens when shared content or site permissions allow the attacker to access other users' content or Teams channels. Cleaning up requires revoking compromised tokens, removing unwanted apps, and auditing permissions thoroughly. Applying the principle of least privilege limits how far an attacker can spread.
Automated flows can be created to copy or forward documents, send data to external endpoints, or change sharing settings on a schedule—behaviors that attackers can weaponize for data theft. Malicious flows can run without obvious user interaction and may bypass standard EDR visibility. When combined with service accounts or compromised credentials, these flows become a low-effort exfiltration channel. Monitoring for new flows, restricting who can create them, and reviewing connectors help reduce this risk. Consider blocking risky connectors and requiring approval for new automation.
Detection should look for unusual file uploads, unexpected sharing link creation, high-volume Graph API calls, and odd patterns of guest invitations or flow creations. Correlating these signals with identity anomalies—like impossible travel or new device usage—helps separate benign from malicious activity. Set alerts for mass downloads, rare admin operations, and sudden permission changes on high-value sites. Regularly review audit logs and use conditional access controls to reduce noisy alerts. Automated playbooks that revoke suspicious links and tokens speed containment.
First, contain the access: revoke tokens, remove unauthorized guests, and disable suspicious apps or flows. Next, snapshot and preserve logs for forensic analysis to trace the scope of access and data accessed. Rotate credentials for impacted accounts and force re-authentication where possible to invalidate sessions. Conduct a focused permission audit on affected sites and implement temporary tighter sharing policies. Finally, communicate with stakeholders and plan a coordinated remediation that includes user education and policy changes.
Limit external sharing by default, use least-privilege permissions, and enforce conditional access with device posture checks. Harden app and delegated permissions for Graph, requiring admin consent for high-risk scopes. Require approvals for Power Platform automation, restrict connectors, and log all flow activity. Implement token protection measures, audit guest accounts regularly, and scan for publicly indexed documents. Regular tabletop exercises and red-team simulations focused on SharePoint help validate controls and response plans.
For a practical checklist on hardening SharePoint and Microsoft 365, see the Palisade SharePoint security checklist.
Yes. Anonymous links, public indexing, or misconfigured guest access allow file access without password theft. Regular audits of external sharing and public content reduce this risk.
MFA helps, but stolen tokens or compromised apps can bypass it. MFA is one layer; token hygiene and conditional access are also essential.
Not necessarily—automation brings business value. Instead, restrict who can create flows, require approvals for connectors, and monitor flow activity.
At minimum quarterly; high-risk environments should review monthly. Remove stale guests and enforce just-in-time access where possible.
Exchange/SharePoint audit logs, Azure AD sign-ins and token logs, Graph API call records, and Power Platform flow logs are critical for reconstruction.
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