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T1090.004 Domain Fronting

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. 1 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.

Item Value
ID T1090.004
Sub-techniques T1090.001, T1090.002, T1090.003, T1090.004
Tactics TA0011
Platforms Linux, Windows, macOS
Version 1.1
Created 14 March 2020
Last Modified 30 March 2023

Procedure Examples

ID Name Description
G0016 APT29 APT29 has used the meek domain fronting plugin for Tor to hide the destination of C2 traffic.5
S0154 Cobalt Strike Cobalt Strike has the ability to accept a value for HTTP Host Header to enable domain fronting.3
S0175 meek meek uses Domain Fronting to disguise the destination of network traffic as another server that is hosted in the same Content Delivery Network (CDN) as the intended destination.
S0699 Mythic Mythic supports domain fronting via custom request headers.2
S0649 SMOKEDHAM SMOKEDHAM has used a fronted domain to obfuscate its hard-coded C2 server domain.4

Mitigations

ID Mitigation Description
M1020 SSL/TLS Inspection If it is possible to inspect HTTPS traffic, the captures can be analyzed for connections that appear to be domain fronting.

Detection

ID Data Source Data Component
DS0029 Network Traffic Network Traffic Content

References

  1. David Fifield, Chang Lan, Rod Hynes, Percy Wegmann, and Vern Paxson. (2015). Blocking-resistant communication through domain fronting. Retrieved November 20, 2017. ↩

  2. Thomas, C. (n.d.). Mythc Documentation. Retrieved March 25, 2022. ↩

  3. Strategic Cyber LLC. (2020, November 5). Cobalt Strike: Advanced Threat Tactics for Penetration Testers. Retrieved April 13, 2021. ↩

  4. FireEye. (2021, June 16). Smoking Out a DARKSIDE Affiliate’s Supply Chain Software Compromise. Retrieved September 22, 2021. ↩

  5. Dunwoody, M. and Carr, N.. (2016, September 27). No Easy Breach DerbyCon 2016. Retrieved October 4, 2016. ↩