Look up Suspicious IP Addresses on DNS Blacklists

Verify and report spammers and hackers

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A DNS blacklist (DNSBL) is a database that contains the IP addresses of malicious hosts on the Internet. These hosts are typically email servers that generate large volumes of unsolicited email messages (spam, see below) or other Internet servers used for network attacks. A DNSBL tracks servers by IP address and also within the Internet Domain Name System (DNS).

DNS blacklists help you to determine whether message senders may be spammers or hackers. You can also report spam and suspicious addresses to a DNSBL for the benefit of others on the Internet. The larger blacklists contain millions of entries.

To use the DNSBL services listed below, type an IP address into the form they provide to look it up in the database. If researching the origin of a spam email, you can obtain its IP address from the email headers.

Finally, note that a DNSBL contains only public addresses, not private IP addresses used on local networks.

What Is Spam?

The term spam refers to unsolicited commercial advertisements distributed online. Most spam comes to people via email, but spam can also be found in online forums.

Spam consumes a tremendous amount of network bandwidth on the Internet. More importantly, it can consume too much of peoples' personal time if not managed properly. Email applications have been enhanced significantly over the years to do a better job of detecting and filtering spam.

Some people also consider Internet advertising (such as pop up browser windows) to be spam. In contrast to true spam, though, these forms of advertising are provided to people in the act of visiting Web sites and are merely a "cost of doing business" to help support those sites' products and services.