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The Five Eyes cybersecurity agencies (CISA, NSA, and others) have issued a joint advisory on Fast Flux, a DNS evasion technique used by cybercriminals and nation-state actors. Fast Flux involves rapidly changing DNS records to hide malicious infrastructure, making it harder to block phishing, malware, ransomware, and botnets.
Types of Fast Flux:
- Single Flux – Rapidly changing IP addresses tied to a domain.
- Double Flux – Changing both IP addresses and authoritative name servers.
You Should Know: Detecting & Mitigating Fast Flux Attacks
1. Detecting Fast Flux Domains
Use DNS query analysis to identify unusual patterns:
Check DNS resolution history using dig dig +short example.com dig +trace malicious-domain.com
2. Analyzing DNS Traffic with Tshark
tshark -r dns_traffic.pcap -Y "dns.flags.response == 1" -T fields -e dns.qry.name -e dns.resp.addr
3. Blocking Fast Flux Domains via Firewall
Linux iptables rule to block known malicious IPs iptables -A INPUT -s 192.168.1.100 -j DROP
4. Monitoring DNS Changes with Python
import dns.resolver
def check_dns_flux(domain, threshold=5):
answers = dns.resolver.resolve(domain, 'A')
if len(answers) > threshold:
print(f"[!] Possible Fast Flux: {domain} has {len(answers)} IPs")
5. Using Threat Intelligence Feeds
Fetch emerging threats list
curl -s https://rules.emergingthreats.net/blockrules/compromised-ips.txt | grep -Eo '([0-9]{1,3}.){3}[0-9]{1,3}'
What Undercode Say
Fast Flux remains a critical threat due to weak DNS security. Organizations must:
– Enforce DNSSEC to prevent DNS spoofing.
– Monitor DNS logs for abnormal TTL changes.
– Deploy AI-based anomaly detection (e.g., Darktrace, Cisco Umbrella).
– Use threat feeds to block malicious domains proactively.
Key Commands for Incident Response:
Check active connections (Linux) netstat -tuln Windows DNS cache inspection ipconfig /displaydns Query passive DNS databases curl "https://api.securitytrails.com/v1/domain/$DOMAIN"
Expected Output:
- Real-time DNS monitoring logs
- Blocked malicious IPs via firewall
- Alerts on Fast Flux domain resolutions
References:
Reported By: Doravanourek 9 – Hackers Feeds
Extra Hub: Undercode MoN
Basic Verification: Pass ✅
