Cross-source coverage
T1090.004 / ATT&CK
Proxy: Domain Fronting
1 rule across 1 source.
From MITRE ATT&CK 19.2
Adversaries may take advantage of routing schemes in Content Delivery Networks (CDNs) and other services which host multiple domains to obfuscate the intended destination of HTTPS traffic or traffic tunneled through HTTPS. Domain fronting involves using different domain names in the SNI field of the TLS header and the Host field of the HTTP header. If both domains are served from the same CDN, then the CDN may route to the address specified in the HTTP header after unwrapping the TLS header. A variation of the the technique, "domainless" fronting, utilizes a SNI field that is left blank; this may allow the fronting to work even when the CDN attempts to validate that the SNI and HTTP Host fields match (if the blank SNI fields are ignored).
For example, if domain-x and domain-y are customers of the same CDN, it is possible to place domain-x in the TLS header and domain-y in the HTTP header. Traffic will appear to be going to domain-x, however the CDN may route it to domain-y.
- Tactics
- Command and Control
- Platforms
- Linux · macOS · Windows · ESXi
- Telemetry
-
NSM:ConnectionsWinEventLog:SysmonNSM:Flowauditd:SYSCALLmacos:unifiedlogmacos:osqueryNSM:Firewallesxi:shell
How MITRE says to detect it DET0196
Domain Fronting Behavior via Mismatched TLS SNI and HTTP Host Headers
Windows Analytic 0564
Suspicious outbound HTTPS connections where the TLS Server Name Indication (SNI) does not match the HTTP Host header, indicating potential use of domain fronting to mask C2 traffic via CDNs.
NSM:ConnectionsTLS handshake + HTTP headersWinEventLog:SysmonEventCode=3, 22
Linux Analytic 0565
Applications such as `curl`, `wget`, or custom binaries initiate HTTPS connections where the TLS SNI is mismatched or absent while HTTP Host targets CDN-available C2 endpoints.
NSM:Flowssl.log + http.logauditd:SYSCALLexecve
macOS Analytic 0566
Unsigned or user-space apps initiate TLS connections with one hostname and HTTP headers requesting a different domain, commonly abused in CDN-resident domain fronting techniques.
macos:unifiedlognetwork, socket, and http logsmacos:osqueryprocess_events
ESXi Analytic 0567
Traffic originating from ESXi hosts or management interfaces displays SNI-to-Host mismatch behavior, particularly anomalous given typical infrastructure communication patterns.
NSM:FirewallTLS/HTTP inspectionesxi:shell/var/log/vmkernel.log, /var/log/vmkwarning.log
SigmaHQ/sigma
1 rule| Detection | Severity | Format |
|---|---|---|
| Potentially Suspicious Azure Front Door Connection | Medium | Sigma |