Fast Flux

Created the Tuesday 23 April 2019. Updated 6 months, 2 weeks ago.

Fast flux is a technique used by botnets to conceal the location of their phishing and malware delivery sites by using a constantly changing network of compromised hosts as proxies. This makes it difficult for law enforcement and other security actors to track down and shut down the sites, as the IP addresses of the sites are constantly changing.

Fast flux is often used in combination with other techniques, such as peer-to-peer networking, distributed command and control, web-based load balancing, and proxy redirection, to make the botnet more resilient to detection and countermeasures. By using these techniques together, the botnet can maintain a high level of operational security and evade detection by security systems.

Technique Identifier

U0907

Technique Tags

Fast flux DNS technique Botnets Phishing Malware delivery sites Compromised hosts Proxies Peer-to-peer networking

Code Snippets

Description

This code uses the dnslib and socket modules to create and send a DNS query for the specified domain name to a DNS server. It then receives a DNS response from the server, modifies the response to include the IP addresses of the compromised hosts that will act as proxies, and sends the modified response back to the client.

This code simulates the operation of a DNS server that is being used for fast flux. In a real-world scenario, the DNS server would be under the control of the botnet, and the domain name and proxy addresses would be generated dynamically.

import dnslib
import socket

# Replace with the IP address of the DNS server
dns_server = "8.8.8.8"

# Replace with the domain name that you control
domain_name = "example.com"

# Replace with the IP addresses of the compromised hosts that will act as proxies
proxy_addresses = ["10.0.0.1", "10.0.0.2", "10.0.0.3"]

# Create a DNS query for the domain name
query = dnslib.DNSRecord.question(domain_name)

# Send the DNS query to the DNS server
dns_socket = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
dns_socket.sendto(query.pack(), (dns_server, 53))

# Receive the DNS response from the DNS server
response = dnslib.DNSRecord.parse(dns_socket.recv(4096))

# Modify the DNS response to include the IP addresses of the compromised hosts
response.add_answer(*dnslib.RR.fromZone("example.com A " + " ".join(proxy_addresses)))

# Send the modified DNS response to the client
dns_socket.sendto(response.pack(), (client_address, client_port))

Additional Resources

External Links

The resources provided below are associated links that will give you even more detailed information and research on current evasion technique. It is important to note that, while these resources may be helpful, it is important to exercise caution when following external links. As always, be careful when clicking on links from unknown sources, as they may lead to malicious content.

Fast Flux 101: How Cybercriminals Improve the Resilience of Their Infrastructure to Evade Detection and Law Enforcement Takedowns