M1021: Restrict Web-Based Content
Restricting web-based content involves enforcing policies and technologies that limit access to potentially malicious websites, unsafe downloads, and unauthorized browser behaviors. This can include URL filtering, download restrictions, script blocking, and extension control to protect against exploitation, phishing, and malware delivery. This mitigation can be implemented through the following measures:
Deploy Web Proxy Filtering:
- Use solutions to filter web traffic based on categories, reputation, and content types. - Enforce policies that block unsafe websites or file types at the gateway level.
Enable DNS-Based Filtering:
- Implement tools to restrict access to domains associated with malware or phishing campaigns. - Use public DNS filtering services to enhance protection.
Enforce Content Security Policies (CSP):
- Configure CSP headers on internal and external web applications to restrict script execution, iframe embedding, and cross-origin requests.
Control Browser Features:
- Disable unapproved browser features like automatic downloads, developer tools, or unsafe scripting. - Enforce policies through tools like Group Policy Management to control browser settings.
Monitor and Alert on Web-Based Threats:
- Use SIEM tools to collect and analyze web proxy logs for signs of anomalous or malicious activity. - Configure alerts for access attempts to blocked domains or repeated file download failures.
Security context for executives and security teams
M1021: Restrict Web-Based Content describes Restricting web-based content involves enforcing policies and technologies that limit access to potentially malicious websites, unsafe downloads, and unauthorized browser behaviors. This can include URL filtering, download restrictions, script blocking, and extension control to protect against exploitation, phishing, and malware delivery. This mitigation can be implemented through the following measures: Deploy Web Proxy Filtering: - Use solutions to filter web traffic based on categories, reputation, and content t...
Executive priority
M1021: Restrict Web-Based Content is an official MITRE ATT&CK mitigation. Glexia treats it as defensive behavior context for prioritizing monitoring, control validation, and response planning without using the object by itself as an attribution claim.
Technical view
Security teams should validate M1021: Restrict Web-Based Content by reviewing the official ATT&CK relationships, mapped tactics (the mapped ATT&CK tactic context), supported platforms (the platforms named in the official object), and available local telemetry before making detection or mitigation decisions.
Likely telemetry
- Official ATT&CK relationships and object metadata
Detection direction
- Validate whether M1021: Restrict Web-Based Content appears in your detection coverage and tabletop scenarios.
- Use the object to align executive risk language with SOC, incident response, and detection engineering work.
- Do not treat ATT&CK relationship context as attribution without corroborating evidence.
Mitigation priorities
- Map the object to existing controls and identify missing telemetry or response ownership.
- Prioritize mitigations that reduce exposure on the listed platforms and tactics.
- Review adjacent ATT&CK relationships before changing policy, detections, or reporting language.
Additional notes and limits
Baseline Glexia take generated from the official MITRE ATT&CK STIX object, source hash, tactics, platforms, and detection fields. It is safe to replace with a richer model-generated take for the same source hash later.
This baseline take is source-grounded and schema-validated, but it does not include environment-specific telemetry, incident evidence, or threat-intelligence corroboration.
Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.
Restrict Web-Based Content
Restricting web-based content involves enforcing policies and technologies that limit access to potentially malicious websites, unsafe downloads, and unauthorized browser behaviors. This can include URL filtering, download restrictions, script blocking, and extension control to protect against exploitation, phishing, and malware delivery. This mitigation can be implemented through the following measures:
Deploy Web Proxy Filtering:
- Use solutions to filter web traffic based on categories, reputation, and content types. - Enforce policies that block unsafe websites or file types at the gateway level.
Enable DNS-Based Filtering:
- Implement tools to restrict access to domains associated with malware or phishing campaigns. - Use public DNS filtering services to enhance protection.
Enforce Content Security Policies (CSP):
- Configure CSP headers on internal and external web applications to restrict script execution, iframe embedding, and cross-origin requests.
Control Browser Features:
- Disable unapproved browser features like automatic downloads, developer tools, or unsafe scripting. - Enforce policies through tools like Group Policy Management to control browser settings.
Monitor and Alert on Web-Based Threats:
- Use SIEM tools to collect and analyze web proxy logs for signs of anomalous or malicious activity. - Configure alerts for access attempts to blocked domains or repeated file download failures.
How security teams should use this page
Treat this object as behavior context, not an attribution claim. Validate the related groups, software, data sources, and mitigations against official ATT&CK relationships and your own telemetry before making control-coverage decisions.
Techniques used
This mirrors the MITRE pattern of making group, software, campaign, and technique relationships scannable. Relationship notes come from mirrored ATT&CK relationship text when available.
| Domain | ID | Name | Relationship / procedure |
|---|---|---|---|
| Enterprise | T1659 | Content Injection | Consider blocking download/transfer and execution of potentially uncommon file types known to be used in adversary campaigns. |
| Enterprise | T1102.002 | Bidirectional CommunicationSub-technique | Web proxies can be used to enforce external network communication policy that prevents use of unauthorized external services. |
| Enterprise | T1566.002 | Spearphishing LinkSub-technique | Determine if certain websites that can be used for spearphishing are necessary for business operations and consider blocking access if activity cannot be monitored well or if it poses a significant risk. |
| Enterprise | T1528 | Steal Application Access Token | Administrators can block end-user consent to OAuth applications, disabling users from authorizing third-party apps through OAuth 2.0 and forcing administrative consent for all requests. They can also block end-user registration of applications by their users, to reduce risk. A Cloud Access Security Broker can also be used to ban applications. Azure offers a couple of enterprise policy settings in the Azure Management Portal that may help: "Users -> User settings -> App registrations: Users can register applications" can be set to "no" to prevent users from registering new applications. "Enterprise applications -> User settings -> Enterprise applications: Users can consent to apps accessing company data on their behalf" can be set to "no" to prevent users from consenting to allow third-party multi-tenant applications |
| Enterprise | T1539 | Steal Web Session Cookie | Restrict or block web-based content that could be used to extract session cookies or credentials stored in browsers. Use browser security settings, such as disabling third-party cookies and restricting browser extensions, to limit the attack surface. |
| Enterprise | T1218.001 | Compiled HTML FileSub-technique | Consider blocking download/transfer and execution of potentially uncommon file types known to be used in adversary campaigns, such as CHM files |
| Enterprise | T1568 | Dynamic Resolution | In some cases a local DNS sinkhole may be used to help prevent behaviors associated with dynamic resolution. |
| Enterprise | T1102.001 | Dead Drop ResolverSub-technique | Web proxies can be used to enforce external network communication policy that prevents use of unauthorized external services. |
| Enterprise | T1204 | User Execution | If a link is being visited by a user, block unknown or unused files in transit by default that should not be downloaded or by policy from suspicious sites as a best practice to prevent some vectors, such as .scr, .exe, .pif, .cpl, etc. Some download scanning devices can open and analyze compressed and encrypted formats, such as zip and rar that may be used to conceal malicious files. |
| Enterprise | T1133 | External Remote Services | Restrict all traffic to and from public Tor nodes. CitationDefending Against Malicious Cyber Activity Originating from Tor |
| Enterprise | T1189 | Drive-by Compromise | Adblockers can help prevent malicious code served through ads from executing in the first place. Script blocking extensions can also help to prevent the execution of JavaScript. Consider disabling browser push notifications from certain applications and browsers.Citationmac security virus popupCitationpush notifications -infosecinstituteCitationsite notifications - krebsonsecurity |
| Enterprise | T1566.003 | Spearphishing via ServiceSub-technique | Determine if certain social media sites, personal webmail services, or other service that can be used for spearphishing is necessary for business operations and consider blocking access if activity cannot be monitored well or if it poses a significant risk. |
| Enterprise | T1567 | Exfiltration Over Web Service | Web proxies can be used to enforce an external network communication policy that prevents use of unauthorized external services. |
| Enterprise | T1568.002 | Domain Generation AlgorithmsSub-technique | In some cases a local DNS sinkhole may be used to help prevent DGA-based command and control at a reduced cost. |
| Enterprise | T1550.001 | Application Access TokenSub-technique | Update corporate policies to restrict what types of third-party applications may be added to any online service or tool that is linked to the company's information, accounts or network (e.g., Google, Microsoft, Dropbox, Basecamp, GitHub). However, rather than providing high-level guidance on this, be extremely specific—include a list of per-approved applications and deny all others not on the list. Administrators may also block end-user consent through administrative portals, such as the Azure Portal, disabling users from authorizing third-party apps through OAuth and forcing administrative consent.CitationMicrosoft Azure AD Admin Consent |
| Enterprise | T1102 | Web Service | Web proxies can be used to enforce external network communication policy that prevents use of unauthorized external services. |
| Enterprise | T1566 | Phishing | Determine if certain websites or attachment types (ex: .scr, .exe, .pif, .cpl, etc.) that can be used for phishing are necessary for business operations and consider blocking access if activity cannot be monitored well or if it poses a significant risk. |
| Enterprise | T1204.004 | Malicious Copy and PasteSub-technique | If a link is being requested by a user, block unknown or unused files in transit by default that should not be downloaded or by policy from suspicious sites as a best practice to prevent some vectors, such as `.scr`, `.exe`, `.pif`, `.cpl`, etc. |
| Enterprise | T1059.005 | Visual BasicSub-technique | Script blocking extensions can help prevent the execution of scripts and HTA files that may commonly be used during the exploitation process. For malicious code served up through ads, adblockers can help prevent that code from executing in the first place. |
| Enterprise | T1102.003 | One-Way CommunicationSub-technique | Web proxies can be used to enforce external network communication policy that prevents use of unauthorized external services. |
| Enterprise | T1127 | Trusted Developer Utilities Proxy Execution | Consider disabling software installation or execution from the internet via developer utilities. |
| Enterprise | T1059.007 | JavaScriptSub-technique | Script blocking extensions can help prevent the execution of JavaScript and HTA files that may commonly be used during the exploitation process. For malicious code served up through ads, adblockers can help prevent that code from executing in the first place. |
| Enterprise | T1555.003 | Credentials from Web BrowsersSub-technique | Restrict or block web-based content that could be used to extract session cookies or credentials stored in browsers. Use browser security settings, such as disabling third-party cookies and restricting browser extensions, to limit the attack surface. |
| Enterprise | T1567.002 | Exfiltration to Cloud StorageSub-technique | Web proxies can be used to enforce an external network communication policy that prevents use of unauthorized external services. |
| Enterprise | T1059 | Command and Scripting Interpreter | Script blocking extensions can help prevent the execution of scripts and HTA files that may commonly be used during the exploitation process. For malicious code served up through ads, adblockers can help prevent that code from executing in the first place. |
| Enterprise | T1218 | System Binary Proxy Execution | Restrict use of certain websites, block downloads/attachments, block Javascript, restrict browser extensions, etc. |
| Enterprise | T1567.001 | Exfiltration to Code RepositorySub-technique | Web proxies can be used to enforce an external network communication policy that prevents use of unauthorized external services. |
| Enterprise | T1127.002 | ClickOnceSub-technique | Disable ClickOnce installations from the internet using the following registry key: `\HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\.NETFramework\Security\TrustManager\PromptingLevel — Internet:Disabled`CitationNetSPI ClickOnce |
| Enterprise | T1204.001 | Malicious LinkSub-technique | If a link is being visited by a user, block unknown or unused files in transit by default that should not be downloaded or by policy from suspicious sites as a best practice to prevent some vectors, such as .scr, .exe, .pif, .cpl, etc. Some download scanning devices can open and analyze compressed and encrypted formats, such as zip and rar that may be used to conceal malicious files. |
| Enterprise | T1566.001 | Spearphishing AttachmentSub-technique | Block unknown or unused attachments by default that should not be transmitted over email as a best practice to prevent some vectors, such as .scr, .exe, .pif, .cpl, etc. Some email scanning devices can open and analyze compressed and encrypted formats, such as zip and rar that may be used to conceal malicious attachments. |
| Enterprise | T1567.003 | Exfiltration to Text Storage SitesSub-technique | Web proxies can be used to enforce an external network communication policy that prevents use of unauthorized external services. |
All related ATT&CK context
Object version and sync metadata
The fields below describe the current mirrored snapshot. When Glexia retains multiple ATT&CK source imports, you can open the table to compare the same object across releases (hashes and MITRE timestamps). For MITRE’s own release notes and roadmap, see ATT&CK resources — Updates.
Imported snapshots across ATT&CK releases(2)
| Release | Bundle imported | Object version | Modified | Status | Raw hash |
|---|---|---|---|---|---|
| 19.2 | 1.1 | Current bundle | ac754c1e0f58… | ||
| 19.1 | 1.1 | Older bundle | ac754c1e0f58… |
Mirrored ATT&CK source object
The raw object is retained through the mirrored ATT&CK source bundle and object hash. The raw endpoint returns the exact object from the mirrored bundle when available.
External references and citations
MITRE external references are preserved separately from Glexia analysis so citations remain traceable to their original source records.
- [1]mitre-attackM1021Open source URL
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