Listen to this Post
Introduction:
Threat intelligence is the cornerstone of modern cybersecurity defense, and leveraging community-driven blocklists is a powerful first line of deterrence. The recent release of the Evil-Domains list by DUDIX CTI provides security professionals with a curated feed of malicious domains, enabling proactive network hardening. This guide will walk you through the technical implementation of this and other blocklists to fortify your DNS infrastructure.
Learning Objectives:
- Understand how to acquire and deploy the Evil-Domains blocklist and similar threat intelligence feeds.
- Configure and harden both Linux (BIND) and Windows (DNS Server) environments to utilize these lists.
- Implement automated update procedures to ensure your defenses remain current against evolving threats.
You Should Know:
1. Acquiring and Preparing the Blocklist
The first step is to download the latest blocklist from the public repository. This can be automated using command-line tools.
Linux/macOS: Download the raw Evil-Domains list from GitHub curl -s https://raw.githubusercontent.com/CyberFlooD/Evil-Domains/main/evil-domains.txt -o /etc/bind/evil-domains.txt Verify the download and check the number of entries wc -l /etc/bind/evil-domains.txt
This command uses `curl` to silently (-s) download the raw text file from the GitHub URL and save it to a local directory commonly used for BIND configurations. The `wc -l` command then counts the number of lines (i.e., domains) in the downloaded file, providing a quick verification that the list was acquired successfully.
2. Configuring BIND9 on Linux for Blocking
Once the list is acquired, it must be integrated into your DNS server configuration. For BIND9, this involves creating a zone file that defines the blocked domains.
Create a new zone file for blackholing
zone "blockeddomain.example" {
type master;
file "/etc/bind/zones/blocked.zone";
};
This snippet is placed in your `named.conf` or an included configuration file. It defines a master zone for the domains you wish to block. The critical part is the associated zone file (blocked.zone), which will define all malicious domains to point to a sinkhole IP (e.g., `127.0.0.1` or 0.0.0.0) instead of their real, malicious IP addresses.
3. Building the BIND9 Zone File
The zone file is where the actual blocking logic is defined. It must be a properly formatted DNS zone file.
; BIND zone file for sinkholing malicious domains $TTL 1h @ IN SOA localhost. admin.localhost. ( 2023091701 ; Serial 1h ; Refresh 30m ; Retry 1w ; Expire 1h ; Negative Cache TTL ) @ IN NS localhost. ; Point all malicious domains to a sinkhole IN A 0.0.0.0 IN AAAA ::0
This zone file configuration is powerful. The Start of Authority (SOA) record defines basic parameters for the zone. The key lines are the wildcard (“) A and AAAA records. These ensure that ANY domain name resolved within this zone will return the sinkhole IP addresses (0.0.0.0 for IPv4 and `::0` for IPv6), effectively blocking traffic to and from it.
4. Automating List Updates with a Script
Threat intelligence is dynamic. Manually updating your blocklist is unsustainable; automation is essential.
!/bin/bash Script: update_blocklist.sh BLOCKLIST_URL="https://raw.githubusercontent.com/CyberFlooD/Evil-Domains/main/evil-domains.txt" LOCAL_PATH="/etc/bind/evil-domains.txt" ZONE_PATH="/etc/bind/zones/blocked.zone" Download latest list curl -s $BLOCKLIST_URL -o $LOCAL_PATH.new Check if the file changed if ! cmp -s $LOCAL_PATH $LOCAL_PATH.new; then mv $LOCAL_PATH.new $LOCAL_PATH Rebuild the zone file from the list echo "\$TTL 1h" > $ZONE_PATH echo "@ IN SOA localhost. admin.localhost. ( $(date +%Y%m%d%H) 1h 30m 1w 1h )" >> $ZONE_PATH echo "@ IN NS localhost." >> $ZONE_PATH echo " IN A 0.0.0.0" >> $ZONE_PATH echo " IN AAAA ::0" >> $ZONE_PATH Reload BIND configuration rndc reload echo "Blocklist and zone updated successfully." else rm $LOCAL_PATH.new echo "No updates found." fi
This Bash script automates the entire process. It downloads the latest list and compares it to the current one. If changes are detected, it rebuilds the zone file from scratch with an updated serial number (using the date) and triggers a reload of the BIND service (rndc reload) without restarting it, ensuring minimal disruption to DNS service.
5. Implementing Blocking on Windows DNS Server
For environments utilizing Windows Server DNS, the process is different and leverages DNS Server Policies.
PowerShell: Create a new DNS Server Query Resolution Policy Add-DnsServerQueryResolutionPolicy -Name "EvilDomainsBlockPolicy" -Action IGNORE -FQDN "EQ,.malicious.com" -PassThru
This PowerShell command creates a new DNS policy named “EvilDomainsBlockPolicy”. The `-Action IGNORE` parameter is crucial—it tells the DNS server to simply drop the query for any FQDN that matches the pattern, preventing resolution and therefore communication. The `-FQDN “EQ,.malicious.com”` is a placeholder; you would need a script to import each domain from the blocklist into a similar policy.
6. Leveraging DNS Firewalls or Proxies (e.g., Pi-hole)
For a more versatile solution that can protect an entire network, dedicated DNS filtering appliances are highly effective.
Example for Pi-hole: Adding a custom blocklist Add the Evil-Domains GitHub raw URL to the Pi-hole admin interface: Settings > Blocklists > Enter URL > Add https://raw.githubusercontent.com/CyberFlooD/Evil-Domains/main/evil-domains.txt
This approach requires no direct command line interaction on the server. Instead, you navigate to the web-based admin interface of your DNS filtering tool (like Pi-hole) and add the URL of the blocklist. The tool will automatically handle the downloading, parsing, and application of the list, blocking queries for any domain on the list for all devices using it as a DNS server.
7. Monitoring and Logging Blocked Queries
Deploying a blocklist is ineffective without monitoring. You must verify it’s working and identify attempted attacks.
Linux (BIND): Check query logs for hits to the blocked zone tail -f /var/log/named/query.log | grep blocked.zone Windows (DNS Server): Get statistics for the blocking policy Get-DnsServerQueryResolutionPolicy -Name "EvilDomainsBlockPolicy" | Get-DnsServerPolicyStatistics
The Linux command tails the BIND query log and filters for any queries that are being resolved by your blocking zone, showing you in real-time what is being blocked. The Windows PowerShell command retrieves statistics for the specific blocking policy, providing data on how many queries have been ignored, which is essential for reporting and threat hunting.
What Undercode Say:
- The strategic value of open-source threat intelligence (OSINT) feeds like Evil-Domains cannot be overstated; they democratize advanced security for organizations of all sizes.
- Automation is non-negotiable. A static blocklist is a useless blocklist within days, if not hours, of its creation due to the rapidly evolving threat landscape.
The release and deployment of the Evil-Domains list highlight a critical shift towards collaborative defense. While the technical steps to implement a DNS blocklist are straightforward, the operational wisdom lies in the maintenance and integration into a broader Security Operations Center (SOC) workflow. Relying on a single source, even a reputable one, creates a single point of failure. A robust defense strategy involves aggregating multiple threat feeds, weighting the confidence of their indicators, and coupling DNS blocking with other security layers like endpoint detection and network monitoring. This layered approach ensures that if one defense is bypassed, others remain to detect and mitigate the threat.
Prediction:
The proliferation of free, high-quality OSINT feeds will force adversaries to adapt rapidly, increasing the use of domain generation algorithms (DGAs), fast-flux networks, and HTTPS-only command and control servers to evade DNS-based detection. This will, in turn, accelerate the adoption of more sophisticated behavioral analysis and encrypted traffic inspection technologies at the network edge, making TLS 1.3 decryption a cornerstone of future threat-hunting platforms. The cat-and-mouse game will escalate from the DNS layer to the application layer.
🎯Let’s Practice For Free:
IT/Security Reporter URL:
Reported By: Ines Wallon – Hackers Feeds
Extra Hub: Undercode MoN
Basic Verification: Pass ✅
