Summary
If your IP is listed on the CBL, the primary indicator is a malware infection or botnet activity. Immediate actions should include stopping all outgoing email, scanning all systems for malware, and securing your network. Contact your ISP or hosting provider for assistance. Delisting requires resolving the underlying issue and cleaning the IP of malicious activity before initiating the process on the CBL website. Implement robust security measures, check for open relays, and ensure a valid PTR record. Implementing SPF, DKIM, and DMARC is crucial for email authentication. If on a shared IP, consider switching to a dedicated one. Once delisted, gradually warm up the IP. Use blocklist lookup tools to monitor your IP's reputation. Understand that CBL focuses on malware and botnets, requiring a security-focused approach, and that repeated listings indicate a persistent underlying problem.
Key findings
- Malware/Botnet: CBL primarily lists IPs infected with malware or involved in botnet activity.
- Immediate Halt: Immediately stop all outgoing email traffic from the affected IP.
- Thorough Scan: Conduct a thorough malware scan of all systems using the listed IP.
- Security First: Addressing the security of the listed IP should be the first priority.
- Authentication: Implement SPF, DKIM, and DMARC for email authentication.
- ISP Contact: Contact your ISP or hosting provider for assistance in identifying the source and guidance.
Key considerations
- Security Measures: Implement robust security measures to prevent future infections.
- Shared IP: If using a shared IP, the actions of other users can impact your reputation.
- Warmup: Gradually warm up the IP address after delisting to rebuild its reputation.
- PTR Record: Ensure your IP has a valid PTR record that matches your sending domain.
- Repeated Listings: Repeated listings indicate a persistent underlying issue that needs to be addressed.
- Blocklist Differences: Understand that CBL focuses on malware and botnets, unlike spam-focused blocklists.
What email marketers say
10 marketer opinions
If your IP address is listed in the CBL (Composite Blocking List), it indicates that your IP has likely been identified as sending malware, hosting a botnet, or engaging in other malicious activities. The immediate response should be to halt all outgoing email traffic. Then, thoroughly investigate the cause, scan all systems for malware, and secure your network. Contact your ISP or hosting provider for assistance. Implement robust security measures, including firewalls and intrusion detection systems, to prevent future infections. Check for open relays on your mail server and ensure your IP has a valid PTR record. If on a shared IP, consider switching to a dedicated one. After delisting, warm up your IP gradually and use blocklist lookup tools to monitor your IP's reputation. Implementing SPF, DKIM, and DMARC is essential for email authentication and improving deliverability.
Key opinions
- Stop Email Traffic: Immediately stop all outgoing email traffic from the affected IP to prevent further damage.
- Malware Scan: Perform a thorough malware scan of all systems using the listed IP address to identify and remove infections.
- Contact ISP: Contact your ISP or hosting provider for assistance in identifying the cause and resolving the issue.
- Security Measures: Implement robust security measures, including firewalls and intrusion detection systems, to prevent future infections.
- PTR Record: Ensure your IP has a valid PTR record that matches your sending domain to establish credibility.
- Email Authentication: Implement SPF, DKIM, and DMARC records to authenticate your emails and improve deliverability.
Key considerations
- Shared IP Risk: If using a shared IP, be aware that the actions of other users can affect your IP's reputation.
- IP Warmup: After delisting, gradually warm up your IP address to rebuild its reputation.
- Blocklist Monitoring: Use blocklist lookup tools to monitor your IP's reputation and identify any potential issues.
- Open Relays: Check and secure your mail server to prevent open relays, which can be exploited by spammers.
- Underlying Cause: Identify and remediate the underlying cause of the CBL listing. Repeated listings indicate a persistent problem.
Marketer view
Email marketer from Email Geeks Forum warns that if using a shared IP, the actions of other users can affect your IP's reputation. Consider switching to a dedicated IP to have more control over your sending reputation.
14 Sep 2022 - Email Geeks Forum
Marketer view
Email marketer from Reddit shares that the immediate action should be to stop all outgoing email traffic from the affected IP. Investigate the source of the malicious activity and secure the system to prevent further issues.
4 Feb 2024 - Reddit
What the experts say
4 expert opinions
If your IP address is listed on the CBL, it's a strong indicator that the IP is infected with malware or part of a botnet. Immediate action involves securing the network and removing the malware. Understanding that the CBL focuses on malware, not just spam, is crucial, and resolving the security issue should be the top priority.
Key opinions
- Malware Infection: CBL listings primarily indicate malware infection or botnet activity.
- Security Priority: Securing the infected network and removing malware is the first priority.
- CBL Focus: CBL's focus is on malware and botnets, requiring a security-focused approach.
Key considerations
- Security Measures: Implement robust security measures to prevent future infections.
- Network Security: Thoroughly review and secure your network to prevent further abuse.
- Different Approach: Understand the specific criteria of the CBL, as it differs from spam-focused blocklists.
Expert view
Expert from Spam Resource emphasizes the critical need to identify and remove the malware infection that caused the CBL listing. Focus on securing the compromised system or network to prevent further abuse.
28 Sep 2022 - Spam Resource
Expert view
Expert from Email Geeks explains that an IP address listed in CBL is likely infected and sending out hostile mail and suggests following the instructions on the CBL page to secure the network.
9 Mar 2022 - Email Geeks
What the documentation says
4 technical articles
If your IP address is listed on the CBL, BRBL, or Spamhaus blocklists, it is critical to first identify and resolve the underlying cause of the listing. This commonly involves addressing malware infections, botnet activity, or spamming issues. After correcting the problem and cleaning the IP of malicious activity, you can initiate the delisting process through the specific blocklist's website. Repeated listings indicate a persistent issue that requires further investigation and resolution.
Key findings
- Resolve Cause: The primary step is to identify and resolve the underlying reason for the IP listing, such as malware or spam.
- Clean IP: The listed IP must be cleaned of any malicious activity before requesting delisting.
- Delisting Process: Initiate the delisting process through the website of the specific blocklist (CBL, Spamhaus, BRBL).
- CBL Listing Reasons: CBL lists IPs primarily for sending malware, acting as command and control, or botnet behavior.
Key considerations
- Persistent Issues: Repeated listings suggest a persistent underlying problem that needs thorough investigation.
- Specific Instructions: Follow the specific removal instructions provided by each blocklist individually.
- Reason for Listing: Determine the reason for listing, and correct it, request removal. But repeated listings may indicate a persistent problem
Technical article
Documentation from CBL Website explains that to delist, the cause of the listing must be resolved. The listed IP must be cleaned of any malicious activity, and then the delisting process can be initiated through their website.
15 Jun 2025 - CBL Website
Technical article
Documentation from Spamhaus Website explains that the first step is identifying why the IP was listed and resolving the underlying issue. Then, follow the removal instructions specific to the Spamhaus list the IP is on.
3 May 2022 - Spamhaus Website
Besides Spamhaus, what blocklists are important for email marketers to monitor?
How can I get delisted from Spamhaus?
How can I get help with a Spamhaus listing delisting?
How do I check Spamhaus for my IP address and understand the listings?
How do I deal with a SORBS listing affecting email deliverability?
What causes an IP to be listed on CBL and how can it be resolved?
