IP addresses are the unique identifiers that connect devices to networks, allowing them to communicate with servers and websites. While most IP addresses facilitate legitimate activities, some can be marked as suspicious or even blacklisted by security platforms and services due to malicious activity. For network administrators and businesses, understanding what makes an IP address suspicious can help them better protect their digital assets and mitigate cyber threats.

An IP can be flagged as suspicious for a variety of reasons, from sending large volumes of spam to using an open proxy to conduct phishing or other fraudulent activities. Some of these activities may also include distributing malware, conducting brute force attacks on accounts or forms, or launching denial-of-service attacks against website visitors. Fraud prevention solutions can detect and block these types of IPs to reduce the risk of data breaches or other financial harm to users.

Building a Suspicious IP Address List to Strengthen Cybersecurity

Using an IP reputation database and an up-to-date firewall defense system can help protect businesses from malicious actors who try to steal critical information. Oftentimes, bad actors change their IPs frequently, so a tool that helps cross-check external lists and regularly update your firewall blacklist is essential to keeping up with them. To learn more about identifying suspicious IPs and preventing cybercrime, read our guide on how to manage a suspicious IP address list. Also, download our study on suspicious IPs to see the most common locations of malicious IP addresses and the registrars that connect them to related domains.