Overview
abuse.ch is a non-profit security research project supported by the University of Bern, Switzerland. Their Combined list aggregates data from multiple abuse.ch threat intelligence feeds, including malware distribution sites and botnet C&C servers.
Being listed here usually means your IP is associated with malicious activity beyond just sending spam.
How It Works
abuse.ch operates several specialized tracking projects for malware distribution sites and botnet command-and-control servers. The Combined list merges data from all these projects, allowing a single query to cover all threat types.
How to Get Delisted
abuse.ch listings are based on security incident evidence. You need to thoroughly clean malware from your server or shut down abused services, then submit a removal request through the abuse.ch website explaining what remediation steps you've taken.