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Dynamic Resolution: Fast Flux DNS
Other sub-techniques of Dynamic Resolution (3)
ID | Name |
---|---|
T1568.001 | Fast Flux DNS |
T1568.002 | Domain Generation Algorithms |
T1568.003 | DNS Calculation |
Adversaries may use Fast Flux DNS to hide a command and control channel behind an array of rapidly changing IP addresses linked to a single domain resolution. This technique uses a fully qualified domain name, with multiple IP addresses assigned to it which are swapped with high frequency, using a combination of round robin IP addressing and short Time-To-Live (TTL) for a DNS resource record.[1][2][3]
The simplest, "single-flux" method, involves registering and de-registering an addresses as part of the DNS A (address) record list for a single DNS name. These registrations have a five-minute average lifespan, resulting in a constant shuffle of IP address resolution.[3]
In contrast, the "double-flux" method registers and de-registers an address as part of the DNS Name Server record list for the DNS zone, providing additional resilience for the connection. With double-flux additional hosts can act as a proxy to the C2 host, further insulating the true source of the C2 channel.
Procedure Examples
Name | Description |
---|---|
gh0st RAT |
gh0st RAT operators have used dynamic DNS to mask the true location of their C2 behind rapidly changing IP addresses.[4] |
Machete | |
njRAT | |
TA505 |
TA505 has used fast flux to mask botnets by distributing payloads across multiple IPs.[7] |
Mitigations
This type of attack technique cannot be easily mitigated with preventive controls since it is based on the abuse of system features.
Detection
In general, detecting usage of fast flux DNS is difficult due to web traffic load balancing that services client requests quickly. In single flux cases only IP addresses change for static domain names. In double flux cases, nothing is static. Defenders such as domain registrars and service providers are likely in the best position for detection.
References
- Mehta, L. (2014, December 17). Fast Flux Networks Working and Detection, Part 1. Retrieved March 6, 2017.
- Mehta, L. (2014, December 23). Fast Flux Networks Working and Detection, Part 2. Retrieved March 6, 2017.
- Albors, Josep. (2017, January 12). Fast Flux networks: What are they and how do they work?. Retrieved March 11, 2020.
- Quinn, J. (2019, March 25). The odd case of a Gh0stRAT variant. Retrieved July 15, 2020.
- The Cylance Threat Research Team. (2017, March 22). El Machete's Malware Attacks Cut Through LATAM. Retrieved September 13, 2019.
- Pascual, C. (2018, November 27). AutoIt-Compiled Worm Affecting Removable Media Delivers Fileless Version of BLADABINDI/njRAT Backdoor. Retrieved June 4, 2019.
- Hiroaki, H. and Lu, L. (2019, June 12). Shifting Tactics: Breaking Down TA505 Group’s Use of HTML, RATs and Other Techniques in Latest Campaigns. Retrieved May 29, 2020.