Blocklists of Suspected Malicious IPs and URLs

Several organizations maintain and publish blocklists (a.k.a blacklists) of IP addresses and URLs of systems and networks suspected in malicious activities on-line. Many of these lists are available for free; some have usage restrictions:

ATLAS from Arbor Networks: Free; registration required by contacting Arbor
CLEAN-MX Realtime Database: Free; XML output available
CYMRU Bogon List: Free
DShield Blocklist: Free
DShield Highly Predictive Blacklist: Free; registration required
EmergingThreats Lists: Free; includes Known Compromised Host List and Control Server Rules
Google Safe Browsing API: Free; programmatic access; restrictions apply
HoneyWhales: Free
hpHosts File: Free; limited automation on request
Malc0de Database: Free
Malware Domain Blocklist: Free for non-commercial use
Malware-Control Blacklist: Commercial service; free licensing options available
MalwareDomainList.com Hosts List: Free
Malware Patrol's Malware Block Lists: Free for non-commercial use
MalwareURL List: Commercial service; free licensing options may be available
Nictatech: Free
ParetoLogic URL Clearing House: Free for non-commerical use; registration required
PhishTank Phish Archive: Free; query database via API
Project Honey Pot's Directory of Malicious IPs: Free; registration required to view more than 25 IPs
Scumware.org: Free
Shadowserver IP and URL Reports: Free; registration and approval required
SpyEye Tracker URLs: Free
SRI Threat Intelligence Lists: Free; re-distribution prohibited
Sucuri Blacklists: Free; blacklists of sites hosting malware and of IPs scanning networks
ThreatStop: Paid; free trial available
URL Blacklist: Paid; first download free
ZeuS Tracker Blocklist and URLs: Free
BLADE Malicious URL Analysis: A free auto-generated list of URLs recently identified as malicious

The lists differ in format, goals, and data-collection methodology. Be sure to read about the list before making use of it.

Any blocklist sources that should be on this list, but are missing? Let me know.

For a listing that includes SPAM blacklists and lookups, take a look at OkamalO's page of Malicious IPs and URL FREE Databases.

My other lists of on-line security resources outline Automated Malware Analysis Services and On-Line Tools for Malicious Website Lookups.